diff --git a/Control/Comonad/Trans/Discont/Lazy.hs b/Control/Comonad/Trans/Discont/Lazy.hs
--- a/Control/Comonad/Trans/Discont/Lazy.hs
+++ b/Control/Comonad/Trans/Discont/Lazy.hs
@@ -9,11 +9,12 @@
 -- Stability   :  provisional
 -- Portability :  portable
 -- 
--- Discont is the Density comonad of a constant functor, just as Cont is a 
--- Codensity monad of a constant functor.
+-- 'Discont' is the density comonad of a constant functor, just as 'Cont' is a 
+-- Codensity monad of a constant functor. (For the definition of Density and
+-- Codensity, see the non-Haskell 98 'adjunctions' package)
 --
--- Note that Discont and Context are isomorphic, but DiscontT and ContextT are
--- not.
+-- Note that while 'Discont' and 'Store' are isomorphic, 'DiscontT' and 'StoreT' 
+-- are not.
 --
 ----------------------------------------------------------------------------
 module Control.Comonad.Trans.Discont.Lazy
diff --git a/Control/Comonad/Trans/Discont/Memo.hs b/Control/Comonad/Trans/Discont/Memo.hs
new file mode 100644
--- /dev/null
+++ b/Control/Comonad/Trans/Discont/Memo.hs
@@ -0,0 +1,20 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Control.Comonad.Trans.Discont.Memo
+-- Copyright   :  (C) 2008-2011 Edward Kmett
+-- License     :  BSD-style (see the file LICENSE)
+--
+-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
+-- Stability   :  provisional
+-- Portability :  portable
+--
+-- The memoizing discontinuation comonad transformer.
+-- This version is lazy; for a strict version, see
+-- "Control.Comonad.Trans.Discont.Strict", which has the same interface.
+--
+----------------------------------------------------------------------------
+module Control.Comonad.Trans.Discont.Memo
+  ( module Control.Comonad.Trans.Discont.Memo.Lazy
+  ) where
+
+import Control.Comonad.Trans.Discont.Memo.Lazy
diff --git a/Control/Comonad/Trans/Discont/Memo/Lazy.hs b/Control/Comonad/Trans/Discont/Memo/Lazy.hs
new file mode 100644
--- /dev/null
+++ b/Control/Comonad/Trans/Discont/Memo/Lazy.hs
@@ -0,0 +1,94 @@
+{-# LANGUAGE CPP, RankNTypes #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Control.Comonad.Trans.Discont.Memo.Lazy
+-- Copyright   :  (C) 2008-2011 Edward Kmett
+-- License     :  BSD-style (see the file LICENSE)
+--
+-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
+-- Stability   :  provisional
+-- Portability :  portable
+-- 
+--
+-- 'Discont' is the density comonad of a constant functor, just as 'Cont' is a 
+-- Codensity monad of a constant functor. (For the definition of Density and
+-- Codensity, see the non-Haskell 98 'adjunctions' package)
+--
+-- Note that while 'Discont' and 'Store' are isomorphic, 'DiscontT' and 'StoreT' 
+-- are not.
+--
+-- Like the memoizing store comonad, version memoizes the result of applying 
+-- the continuation to the current context. 
+--
+----------------------------------------------------------------------------
+module Control.Comonad.Trans.Discont.Memo.Lazy
+  ( 
+  -- * The 'discontinuation' comonad
+    Discont
+  , discont
+  -- * The discontinuation comonad transformer
+  , runDiscont
+  , DiscontT
+  , discontT 
+  , runDiscontT
+  -- * Combinators
+  , callCV
+  , label
+  ) where
+
+import Data.Functor.Identity
+import Control.Comonad
+import Control.Comonad.Trans.Class
+
+#ifdef __GLASGOW_HASKELL__
+import Data.Typeable
+
+instance (Typeable s, Typeable1 w) => Typeable1 (DiscontT s w) where
+  typeOf1 dswa = mkTyConApp discontTTyCon [typeOf (s dswa), typeOf1 (w dswa)]
+    where 
+      s :: DiscontT s w a -> s
+      s = undefined
+      w :: DiscontT s w a -> w a
+      w = undefined
+
+discontTTyCon :: TyCon
+discontTTyCon = mkTyCon "Control.Comonad.Trans.Discont.Memo.Lazy.DiscontT" 
+{-# NOINLINE discontTTyCon #-}
+
+#endif
+
+type Discont s = DiscontT s Identity
+
+data DiscontT s w a = DiscontT (w s -> a) (w s) a
+
+discont :: (s -> a) -> s -> Discont s a 
+discont f s = DiscontT (f . runIdentity) (Identity s) (f s)
+
+discontT :: (w s -> a) -> w s -> DiscontT s w a 
+discontT f s = DiscontT f s (f s)
+
+runDiscont :: Discont s a -> (s -> a, s) 
+runDiscont ~(DiscontT f (Identity s) _) = (f . Identity,  s)
+
+runDiscontT :: DiscontT s w a -> (w s -> a, w s)
+runDiscontT ~(DiscontT f s _) = (f, s)
+
+instance Functor (DiscontT s w) where
+  fmap g ~(DiscontT f ws a) = DiscontT (g . f) ws (g a)
+
+instance Extend (DiscontT s w) where
+  duplicate ~(DiscontT f ws _) = discontT (discontT f) ws
+
+instance Comonad (DiscontT s w) where
+  extract ~(DiscontT _ _ a) = a
+
+instance ComonadTrans (DiscontT s) where
+  lower ~(DiscontT f s _) = extend f s
+
+-- instance Apply w => Apply (DiscontT s w) where
+
+label :: Comonad w => DiscontT s w a -> s 
+label ~(DiscontT _ ws _) = extract ws
+
+callCV :: DiscontT s w (DiscontT s w (DiscontT s w a -> a) -> b) -> b
+callCV ~(DiscontT k s _) = k s (discontT (\s' ~(DiscontT k' _ _) -> k' s') s)
diff --git a/Control/Comonad/Trans/Discont/Memo/Strict.hs b/Control/Comonad/Trans/Discont/Memo/Strict.hs
new file mode 100644
--- /dev/null
+++ b/Control/Comonad/Trans/Discont/Memo/Strict.hs
@@ -0,0 +1,94 @@
+{-# LANGUAGE CPP, RankNTypes #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Control.Comonad.Trans.Discont.Memo.Strict
+-- Copyright   :  (C) 2008-2011 Edward Kmett
+-- License     :  BSD-style (see the file LICENSE)
+--
+-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
+-- Stability   :  provisional
+-- Portability :  portable
+-- 
+--
+-- 'Discont' is the density comonad of a constant functor, just as 'Cont' is a 
+-- Codensity monad of a constant functor. (For the definition of Density and
+-- Codensity, see the non-Haskell 98 'adjunctions' package)
+--
+-- Note that while 'Discont' and 'Store' are isomorphic, 'DiscontT' and 'StoreT' 
+-- are not.
+--
+-- Like the memoizing store comonad, version memoizes the result of applying 
+-- the continuation to the current context. 
+--
+----------------------------------------------------------------------------
+module Control.Comonad.Trans.Discont.Memo.Strict
+  ( 
+  -- * The 'discontinuation' comonad
+    Discont
+  , discont
+  -- * The discontinuation comonad transformer
+  , runDiscont
+  , DiscontT
+  , discontT 
+  , runDiscontT
+  -- * Combinators
+  , callCV
+  , label
+  ) where
+
+import Data.Functor.Identity
+import Control.Comonad
+import Control.Comonad.Trans.Class
+
+#ifdef __GLASGOW_HASKELL__
+import Data.Typeable
+
+instance (Typeable s, Typeable1 w) => Typeable1 (DiscontT s w) where
+  typeOf1 dswa = mkTyConApp discontTTyCon [typeOf (s dswa), typeOf1 (w dswa)]
+    where 
+      s :: DiscontT s w a -> s
+      s = undefined
+      w :: DiscontT s w a -> w a
+      w = undefined
+
+discontTTyCon :: TyCon
+discontTTyCon = mkTyCon "Control.Comonad.Trans.Discont.Memo.Strict.DiscontT" 
+{-# NOINLINE discontTTyCon #-}
+
+#endif
+
+type Discont s = DiscontT s Identity
+
+data DiscontT s w a = DiscontT (w s -> a) (w s) a
+
+discont :: (s -> a) -> s -> Discont s a 
+discont f s = DiscontT (f . runIdentity) (Identity s) (f s)
+
+discontT :: (w s -> a) -> w s -> DiscontT s w a 
+discontT f s = DiscontT f s (f s)
+
+runDiscont :: Discont s a -> (s -> a, s) 
+runDiscont (DiscontT f (Identity s) _) = (f . Identity,  s)
+
+runDiscontT :: DiscontT s w a -> (w s -> a, w s)
+runDiscontT (DiscontT f s _) = (f, s)
+
+instance Functor (DiscontT s w) where
+  fmap g (DiscontT f ws a) = DiscontT (g . f) ws (g a)
+
+instance Extend (DiscontT s w) where
+  duplicate (DiscontT f ws _) = discontT (discontT f) ws
+
+instance Comonad (DiscontT s w) where
+  extract (DiscontT _ _ a) = a
+
+instance ComonadTrans (DiscontT s) where
+  lower (DiscontT f s _) = extend f s
+
+-- instance Apply w => Apply (DiscontT s w) where
+
+label :: Comonad w => DiscontT s w a -> s 
+label (DiscontT _ ws _) = extract ws
+
+callCV :: DiscontT s w (DiscontT s w (DiscontT s w a -> a) -> b) -> b
+callCV (DiscontT k s _) = k s (discontT (\s' (DiscontT k' _ _) -> k' s') s)
diff --git a/Control/Comonad/Trans/Discont/Strict.hs b/Control/Comonad/Trans/Discont/Strict.hs
--- a/Control/Comonad/Trans/Discont/Strict.hs
+++ b/Control/Comonad/Trans/Discont/Strict.hs
@@ -8,13 +8,13 @@
 -- Maintainer  :  Edward Kmett <ekmett@gmail.com>
 -- Stability   :  provisional
 -- Portability :  portable
--- 
--- Discont is the Density comonad of a constant functor, just as Cont is a 
--- Codensity monad of a constant functor.
 --
--- Note that Discont and Context are isomorphic, but DiscontT and ContextT are
--- not.
+-- 'Discont' is the density comonad of a constant functor, just as 'Cont' is a 
+-- Codensity monad of a constant functor. (For the definition of Density and
+-- Codensity, see the non-Haskell 98 'adjunctions' package)
 --
+-- Note that while 'Discont' and 'Store' are isomorphic, 'DiscontT' and 'StoreT' 
+-- are not.
 ----------------------------------------------------------------------------
 module Control.Comonad.Trans.Discont.Strict
   ( 
diff --git a/Control/Comonad/Trans/Store/Memo.hs b/Control/Comonad/Trans/Store/Memo.hs
new file mode 100644
--- /dev/null
+++ b/Control/Comonad/Trans/Store/Memo.hs
@@ -0,0 +1,21 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Control.Comonad.Trans.Store.Memo
+-- Copyright   :  (C) 2008-2011 Edward Kmett
+-- License     :  BSD-style (see the file LICENSE)
+--
+-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
+-- Stability   :  provisional
+-- Portability :  portable
+--
+-- The memoized store comonad transformer (aka costate).
+--
+-- This version is lazy; for a strict version, see
+-- "Control.Comonad.Trans.Store.Memo.Strict", which has the same interface.
+--
+----------------------------------------------------------------------------
+module Control.Comonad.Trans.Store.Memo
+  ( module Control.Comonad.Trans.Store.Memo.Lazy
+  ) where
+
+import Control.Comonad.Trans.Store.Memo.Lazy
diff --git a/Control/Comonad/Trans/Store/Memo/Lazy.hs b/Control/Comonad/Trans/Store/Memo/Lazy.hs
new file mode 100644
--- /dev/null
+++ b/Control/Comonad/Trans/Store/Memo/Lazy.hs
@@ -0,0 +1,102 @@
+{-# LANGUAGE CPP #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Control.Comonad.Trans.Store.Memo.Lazy
+-- Copyright   :  (C) 2008-2011 Edward Kmett
+-- License     :  BSD-style (see the file LICENSE)
+--
+-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
+-- Stability   :  provisional
+-- Portability :  portable
+--
+-- The lazy store (state-in-context/costate) comonad transformer is subject to the laws:
+-- 
+-- > x = put (get x) x
+-- > y = get (put y x)
+-- > put y x = put y (put z x)
+--
+-- This version of the transformer lazily memoizes the result of applying the 
+-- comonad to the current state. This can be useful for avoiding redundant 
+-- computation if you reuse the same StoreT object multiple times.
+----------------------------------------------------------------------------
+module Control.Comonad.Trans.Store.Memo.Lazy
+  ( 
+  -- * The Store comonad
+    Store, store, runStore
+  -- * The Store comonad transformer
+  , StoreT, storeT, runStoreT
+  -- * Operations
+  , get
+  , put
+  , modify
+  , experiment
+  ) where
+
+import Control.Comonad
+import Control.Comonad.Hoist.Class
+import Control.Comonad.Trans.Class
+import Data.Functor.Identity
+
+#ifdef __GLASGOW_HASKELL__
+import Data.Typeable
+instance (Typeable s, Typeable1 w) => Typeable1 (StoreT s w) where
+  typeOf1 dswa = mkTyConApp storeTTyCon [typeOf (s dswa), typeOf1 (w dswa)]
+    where
+      s :: StoreT s w a -> s
+      s = undefined
+      w :: StoreT s w a -> w a
+      w = undefined
+
+instance (Typeable s, Typeable1 w, Typeable a) => Typeable (StoreT s w a) where
+  typeOf = typeOfDefault
+
+storeTTyCon :: TyCon
+storeTTyCon = mkTyCon "Control.Comonad.Trans.Store.Memo.Lazy.StoreT"
+{-# NOINLINE storeTTyCon #-}
+#endif
+
+type Store s = StoreT s Identity
+
+store :: (s -> a) -> s -> Store s a 
+store f s = StoreT (Identity f) s (Identity (f s))
+
+runStore :: Store s a -> (s -> a, s)
+runStore ~(StoreT (Identity f) s _) = (f, s)
+
+-- inhabitants of @StoreT wf s w@ ensure that
+--
+-- > w = ($s) <$> wf
+data StoreT s w a = StoreT (w (s -> a)) s (w a)
+
+runStoreT :: StoreT s w a -> (w (s -> a), s)
+runStoreT ~(StoreT wf s _) = (wf, s)
+
+storeT :: Functor w => w (s -> a) -> s -> StoreT s w a
+storeT wf s = StoreT wf s (fmap ($s) wf)
+
+instance Functor w => Functor (StoreT s w) where
+  fmap f ~(StoreT wf s w) = StoreT (fmap (f .) wf) s (fmap f w)
+
+instance Extend w => Extend (StoreT s w) where
+  duplicate ~(StoreT wf s _) = storeT (extend storeT wf) s 
+
+instance Comonad w => Comonad (StoreT s w) where
+  extract ~(StoreT _ _ w) = extract w
+
+instance ComonadTrans (StoreT s) where
+  lower ~(StoreT _ _ w) = w
+
+instance ComonadHoist (StoreT s) where
+  cohoist ~(StoreT f s w) = StoreT (Identity (extract f)) s (Identity (extract w))
+
+get :: StoreT s w a -> s
+get ~(StoreT _ s _) = s
+
+put :: Comonad w => s -> StoreT s w a -> a 
+put s ~(StoreT f _ _) = extract f s
+
+modify :: Comonad w => (s -> s) -> StoreT s w a -> a
+modify f ~(StoreT g s _) = extract g (f s)
+
+experiment :: (Comonad w, Functor f) => f (s -> s) -> StoreT s w a -> f a
+experiment fs ~(StoreT g s _) = fmap (\f -> extract g (f s)) fs
diff --git a/Control/Comonad/Trans/Store/Memo/Strict.hs b/Control/Comonad/Trans/Store/Memo/Strict.hs
new file mode 100644
--- /dev/null
+++ b/Control/Comonad/Trans/Store/Memo/Strict.hs
@@ -0,0 +1,102 @@
+{-# LANGUAGE CPP #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Control.Comonad.Trans.Store.Memo.Strict
+-- Copyright   :  (C) 2008-2011 Edward Kmett
+-- License     :  BSD-style (see the file LICENSE)
+--
+-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
+-- Stability   :  provisional
+-- Portability :  portable
+--
+-- The lazy store (state-in-context/costate) comonad transformer is subject to the laws:
+-- 
+-- > x = put (get x) x
+-- > y = get (put y x)
+-- > put y x = put y (put z x)
+--
+-- This version of the transformer lazily memoizes the result of applying the 
+-- comonad to the current state. This can be useful for avoiding redundant 
+-- computation if you reuse the same StoreT object multiple times.
+----------------------------------------------------------------------------
+module Control.Comonad.Trans.Store.Memo.Strict
+  ( 
+  -- * The Store comonad
+    Store, store, runStore
+  -- * The Store comonad transformer
+  , StoreT, storeT, runStoreT
+  -- * Operations
+  , get
+  , put
+  , modify
+  , experiment
+  ) where
+
+import Control.Comonad
+import Control.Comonad.Hoist.Class
+import Control.Comonad.Trans.Class
+import Data.Functor.Identity
+
+#ifdef __GLASGOW_HASKELL__
+import Data.Typeable
+instance (Typeable s, Typeable1 w) => Typeable1 (StoreT s w) where
+  typeOf1 dswa = mkTyConApp storeTTyCon [typeOf (s dswa), typeOf1 (w dswa)]
+    where
+      s :: StoreT s w a -> s
+      s = undefined
+      w :: StoreT s w a -> w a
+      w = undefined
+
+instance (Typeable s, Typeable1 w, Typeable a) => Typeable (StoreT s w a) where
+  typeOf = typeOfDefault
+
+storeTTyCon :: TyCon
+storeTTyCon = mkTyCon "Control.Comonad.Trans.Store.Memo.Strict.StoreT"
+{-# NOINLINE storeTTyCon #-}
+#endif
+
+type Store s = StoreT s Identity
+
+store :: (s -> a) -> s -> Store s a 
+store f s = StoreT (Identity f) s (Identity (f s))
+
+runStore :: Store s a -> (s -> a, s)
+runStore (StoreT (Identity f) s _) = (f, s)
+
+-- inhabitants of @StoreT wf s w@ ensure that
+--
+-- > w = ($s) <$> wf
+data StoreT s w a = StoreT (w (s -> a)) s (w a)
+
+runStoreT :: StoreT s w a -> (w (s -> a), s)
+runStoreT (StoreT wf s _) = (wf, s)
+
+storeT :: Functor w => w (s -> a) -> s -> StoreT s w a
+storeT wf s = StoreT wf s (fmap ($s) wf)
+
+instance Functor w => Functor (StoreT s w) where
+  fmap f (StoreT wf s w) = StoreT (fmap (f .) wf) s (fmap f w)
+
+instance Extend w => Extend (StoreT s w) where
+  duplicate (StoreT wf s _) = storeT (extend storeT wf) s 
+
+instance Comonad w => Comonad (StoreT s w) where
+  extract (StoreT _ _ w) = extract w
+
+instance ComonadTrans (StoreT s) where
+  lower (StoreT _ _ w) = w
+
+instance ComonadHoist (StoreT s) where
+  cohoist (StoreT f s w) = StoreT (Identity (extract f)) s (Identity (extract w))
+
+get :: StoreT s w a -> s
+get (StoreT _ s _) = s
+
+put :: Comonad w => s -> StoreT s w a -> a 
+put s (StoreT f _ _) = extract f s
+
+modify :: Comonad w => (s -> s) -> StoreT s w a -> a
+modify f (StoreT g s _) = extract g (f s)
+
+experiment :: (Comonad w, Functor f) => f (s -> s) -> StoreT s w a -> f a
+experiment fs (StoreT g s _) = fmap (\f -> extract g (f s)) fs
diff --git a/comonad-transformers.cabal b/comonad-transformers.cabal
--- a/comonad-transformers.cabal
+++ b/comonad-transformers.cabal
@@ -1,6 +1,6 @@
 name:          comonad-transformers
 category:      Control, Comonads
-version:       1.0.0
+version:       1.0.1
 license:       BSD3
 cabal-version: >= 1.6
 license-file:  LICENSE
@@ -44,6 +44,9 @@
     Control.Comonad.Trans.Discont
     Control.Comonad.Trans.Discont.Lazy
     Control.Comonad.Trans.Discont.Strict
+    Control.Comonad.Trans.Discont.Memo
+    Control.Comonad.Trans.Discont.Memo.Lazy
+    Control.Comonad.Trans.Discont.Memo.Strict
     Control.Comonad.Trans.Env
     Control.Comonad.Trans.Env.Lazy
     Control.Comonad.Trans.Env.Strict
@@ -51,6 +54,9 @@
     Control.Comonad.Trans.Store
     Control.Comonad.Trans.Store.Lazy
     Control.Comonad.Trans.Store.Strict
+    Control.Comonad.Trans.Store.Memo
+    Control.Comonad.Trans.Store.Memo.Lazy
+    Control.Comonad.Trans.Store.Memo.Strict
     Control.Comonad.Trans.Traced
     Control.Comonad.Trans.Stream
     Data.Functor.Coproduct