The zippo package
This light-weight library provides a basic, but fully-type-checked zipper implementation, suitable for any algebraic data structure. Our implementation has no notion of "left" and "right", and instead uses lenses (from the yall package) to indicate directions to "navigate down to".
For a similar approach with many more features, but less type-safety see pez.
UPDATE: I have stopped developing this package; instead look into lens v3.0 which includes similar functionality
CHANGES: 0.2 to 0.3:
depend on new yall, depending on new categories
|Versions||0.1, 0.2, 0.3|
|Dependencies||base (4.*), mtl (≥2), yall (≥0.2.1)|
|Source repository||git clone https://github.com/jberryman/zippo.git|
|Upload date||Fri Sep 21 16:44:12 UTC 2012|
|Build failure||ghc-7.6 (log)|