diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright 2011 Edward Kmett
+Copyright 2011-2013 Edward Kmett
 
 All rights reserved.
 
@@ -12,10 +12,6 @@
 2. 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.
-
-3. Neither the name of the author nor the names of his contributors
-   may be used to endorse or promote products derived from this software
-   without specific prior written permission.
 
 THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
diff --git a/semigroups.cabal b/semigroups.cabal
--- a/semigroups.cabal
+++ b/semigroups.cabal
@@ -1,6 +1,6 @@
 name:          semigroups
 category:      Algebra, Data, Data Structures, Math
-version:       0.10
+version:       0.11
 license:       BSD3
 cabal-version: >= 1.10
 license-file:  LICENSE
@@ -9,11 +9,9 @@
 stability:     provisional
 homepage:      http://github.com/ekmett/semigroups/
 bug-reports:   http://github.com/ekmett/semigroups/issues
-copyright:     Copyright (C) 2011 Edward A. Kmett
-synopsis:      Haskell 98 semigroups
+copyright:     Copyright (C) 2011-2013 Edward A. Kmett
+synopsis:      Anything that associates
 description:
-    Haskell 98 semigroups
-    .
     In mathematics, a semigroup is an algebraic structure consisting of a set together with an associative binary operation. A semigroup generalizes a monoid in that there might not exist an identity element. It also (originally) generalized a group (a monoid with all inverses) to a type where every element did not have to have an inverse, thus the name semigroup.
 build-type:    Simple
 extra-source-files: .travis.yml README.markdown
diff --git a/src/Data/List/NonEmpty.hs b/src/Data/List/NonEmpty.hs
--- a/src/Data/List/NonEmpty.hs
+++ b/src/Data/List/NonEmpty.hs
@@ -5,7 +5,7 @@
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.List.NonEmpty
--- Copyright   :  (C) 2011 Edward Kmett,
+-- Copyright   :  (C) 2011-2013 Edward Kmett,
 --                (C) 2010 Tony Morris, Oliver Taylor, Eelis van der Weegen
 -- License     :  BSD-style (see the file LICENSE)
 --
@@ -36,6 +36,7 @@
    , init        -- :: NonEmpty a -> [a]
    , (<|), cons  -- :: a -> NonEmpty a -> NonEmpty a
    , uncons      -- :: NonEmpty a -> (a, Maybe (NonEmpty a))
+   , unfoldr     -- :: (a -> (b, Maybe a)) -> a -> NonEmpty b
    , sort        -- :: NonEmpty a -> NonEmpty a
    , reverse     -- :: NonEmpty a -> NonEmpty a
    , inits       -- :: Foldable f => f a -> NonEmpty a
@@ -153,6 +154,13 @@
 uncons :: NonEmpty a -> (a, Maybe (NonEmpty a))
 uncons ~(a :| as) = (a, nonEmpty as)
 {-# INLINE uncons #-}
+
+unfoldr :: (a -> (b, Maybe a)) -> a -> NonEmpty b
+unfoldr f a = case f a of
+  (b, mc) -> b :| maybe [] go mc
+ where
+    go c = case f c of
+      (d, me) -> d : maybe [] go me
 
 instance Functor NonEmpty where
   fmap f ~(a :| as) = f a :| fmap f as
diff --git a/src/Data/Semigroup.hs b/src/Data/Semigroup.hs
--- a/src/Data/Semigroup.hs
+++ b/src/Data/Semigroup.hs
@@ -9,7 +9,7 @@
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Semigroup
--- Copyright   :  (C) 2011 Edward Kmett,
+-- Copyright   :  (C) 2011-2013 Edward Kmett,
 -- License     :  BSD-style (see the file LICENSE)
 --
 -- Maintainer  :  Edward Kmett <ekmett@gmail.com>
@@ -80,6 +80,7 @@
 import Data.Text.Lazy as Lazy
 import Data.Hashable
 import Data.HashMap.Lazy as Lazy
+import Data.HashSet
 #endif
 
 #ifdef LANGUAGE_DeriveDataTypeable
@@ -291,6 +292,10 @@
 
 instance (Hashable k, Eq k) => Semigroup (Lazy.HashMap k a) where
   (<>) = mappend
+
+instance (Hashable a, Eq a) => Semigroup (HashSet a) where
+  (<>) = mappend
+  times1p _ a = a
 #endif
 
 -- | Provide a Semigroup for an arbitrary Monoid.