diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright (c) 2013, Chris Done
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Chris Done nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/data-extra.cabal b/data-extra.cabal
new file mode 100644
--- /dev/null
+++ b/data-extra.cabal
@@ -0,0 +1,18 @@
+name:                data-extra
+version:             1.0.0
+synopsis:            Extra utilities for working on Data.* types.
+description:         Extra utilities for working on Data.* types.
+license:             BSD3
+license-file:        LICENSE
+author:              Chris Done
+maintainer:          chrisdone@gmail.com
+copyright:           2013 Chris Done
+category:            Data
+build-type:          Simple
+cabal-version:       >=1.8
+
+library
+  exposed-modules:   Data.Either.Extra, Data.Maybe.Extra
+  hs-source-dirs:    src/
+  build-depends:     base > 4 && <5
+  ghc-options:       -Wall
diff --git a/src/Data/Either/Extra.hs b/src/Data/Either/Extra.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Either/Extra.hs
@@ -0,0 +1,35 @@
+-- | Extra functions for dealing with Either.
+
+module Data.Either.Extra where
+
+-- | A map for Either values.
+mapEither :: (a -> b1) -> (b -> b2) -> Either a b -> Either b1 b2
+mapEither l r = either (Left . l) (Right . r)
+
+-- | Maybe get the left side of an Either.
+leftToMaybe :: Either a b -> Maybe a
+leftToMaybe = either Just (const Nothing)
+
+-- | Maybe get the right side of an Either.
+rightToMaybe :: Either a b -> Maybe b
+rightToMaybe = either (const Nothing) Just
+
+-- | Is a value Left?
+isLeft :: Either a b -> Bool
+isLeft (Left _) = True
+isLeft (Right _) = False
+
+-- | Is a value Right?
+isRight :: Either a b -> Bool
+isRight (Left _) = False
+isRight (Right _) = True
+
+-- | Extract the left value or a default.
+fromLeft :: a -> Either a b -> a
+fromLeft _ (Left x) = x
+fromLeft x _ = x
+
+-- | Extract the right value or a default.
+fromRight :: b -> Either a b -> b
+fromRight _ (Right x) = x
+fromRight x _ = x
diff --git a/src/Data/Maybe/Extra.hs b/src/Data/Maybe/Extra.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Maybe/Extra.hs
@@ -0,0 +1,10 @@
+-- | Extra functions for dealing with Maybe.
+
+module Data.Maybe.Extra where
+
+import Control.Monad
+
+-- | When the predicate is true, return maybe the action's return value.
+whenMaybe :: Monad m => Bool -> m a -> m (Maybe a)
+whenMaybe False _ = return Nothing
+whenMaybe True m = liftM Just m