diff --git a/Data/Octree.hs b/Data/Octree.hs
--- a/Data/Octree.hs
+++ b/Data/Octree.hs
@@ -12,4 +12,5 @@
 
 import Prelude hiding(lookup)
 import Data.Octree.Internal
+import Data.Octree.Instances()
 
diff --git a/Data/Octree/Instances.hs b/Data/Octree/Instances.hs
new file mode 100644
--- /dev/null
+++ b/Data/Octree/Instances.hs
@@ -0,0 +1,40 @@
+module Data.Octree.Instances where
+
+import Data.Octree.Internal
+
+-- Additional instances for convenience
+
+import Data.Functor
+import Data.Foldable hiding(foldr1)
+import Data.Traversable
+
+import Data.Monoid
+
+instance Functor Octree where
+  fmap f (Leaf l) = Leaf . fmap (\(c, a) -> (c, f a)) $  l
+  fmap f (Node { split = sp,
+                 nwu   = anwu,
+                 nwd   = anwd,
+                 neu   = aneu,
+                 ned   = aned,
+                 swu   = aswu,
+                 swd   = aswd,
+                 seu   = aseu,
+                 sed   = ased }) = Node { split = sp,
+                                          nwu   = fmap f anwu,
+                                          nwd   = fmap f anwd,
+                                          neu   = fmap f aneu,
+                                          ned   = fmap f aned,
+                                          swu   = fmap f aswu,
+                                          swd   = fmap f aswd,
+                                          seu   = fmap f aseu,
+                                          sed   = fmap f ased }
+
+-- TODO: test Foldable instance
+instance Foldable Octree where
+  foldMap f (Leaf l)                = foldMap (f . snd) l
+  foldMap f n@(Node { split = sp }) = Prelude.foldr1 mappend . map (foldMap f) . subnodes $ n
+
+-- TODO: test Traversable instance
+--instance Traversable where
+
diff --git a/Data/Octree/Internal.hs b/Data/Octree/Internal.hs
--- a/Data/Octree/Internal.hs
+++ b/Data/Octree/Internal.hs
@@ -6,7 +6,8 @@
                             octreeStep, octantDistance, splitBy', joinStep, splitStep, allOctants, octantDistance',
                             cmp,
                             pickClosest,
-                            depth, size
+                            depth, size,
+                            subnodes
                             ) where
 
 import Data.Vector.V3
@@ -33,26 +34,6 @@
 data Octree a = Node { split :: Vector3,
                        nwu, nwd, neu, ned, swu, swd, seu, sed :: Octree a } |
                 Leaf { unLeaf :: [(Vector3, a)] }  deriving (Show)
-
-instance Functor Octree where
-  fmap f (Leaf l) = Leaf . fmap (Control.Arrow.second f) $  l
-  fmap f (Node { split = sp,
-                 nwu   = anwu,
-                 nwd   = anwd,
-                 neu   = aneu,
-                 ned   = aned,
-                 swu   = aswu,
-                 swd   = aswd,
-                 seu   = aseu,
-                 sed   = ased }) = Node { split = sp,
-                                          nwu   = fmap f anwu,
-                                          nwd   = fmap f anwd,
-                                          neu   = fmap f aneu,
-                                          ned   = fmap f aned,
-                                          swu   = fmap f aswu,
-                                          swd   = fmap f aswd,
-                                          seu   = fmap f aseu,
-                                          sed   = fmap f ased }
 
 -- | Enumerated type to indicate octants in 3D-space relative to given center.
 data ODir = SWD | SED | NWD | NED | SWU | SEU | NWU | NEU deriving (Eq, Ord, Enum, Show, Bounded)
diff --git a/Octree.cabal b/Octree.cabal
--- a/Octree.cabal
+++ b/Octree.cabal
@@ -1,5 +1,5 @@
 name:                Octree
-version:             0.5
+version:             0.5.1
 stability:           beta
 homepage:            https://github.com/mgajda/octree
 package-url:         http://hackage.haskell.org/package/octree
@@ -26,7 +26,7 @@
 Library
    build-depends:    base>=4.0 && < 4.7, AC-Vector >= 2.3.0, QuickCheck >= 2.4.0
    exposed-modules:  Data.Octree
-   other-modules:    Data.Octree.Internal
+   other-modules:    Data.Octree.Internal, Data.Octree.Instances
    exposed:          True
    extensions:       ScopedTypeVariables
 
@@ -36,9 +36,9 @@
   Main-is:           tests/test_Octree.hs
 
 Test-suite readme
-  type:           exitcode-stdio-1.0
+  type:           exitcode-stdio-1.0
   -- We have a symlink: README.lhs -> README.md
-  main-is:        README.lhs
+  main-is:        README.lhs
   Build-depends:  base>=4.0 && < 4.7, AC-Vector >= 2.3.0, QuickCheck >= 2.4.0, markdown-unlit
-  ghc-options:    -pgmL markdown-unlit
+  ghc-options:    -pgmL markdown-unlit
 
diff --git a/tests/test_Octree.hs b/tests/test_Octree.hs
--- a/tests/test_Octree.hs
+++ b/tests/test_Octree.hs
@@ -2,6 +2,7 @@
 module Main(main) where
 
 import Data.Octree.Internal
+import Data.Octree.Instances()
 --import Data.Octree() -- test that interface module is not broken
 import Prelude hiding(lookup)
 import Data.List(sort, sortBy)