I love itertools; it's one of the most beautiful, composable standard libs. Whenever I have an iteration problem, there's almost always an itertools routine that fits it perfectly. Sometimes, however, neither itertools nor the recipes included in its docs do quite what I need.
Here I've collected several routines I've reached for but not found. Since they are deceptively tricky to get right, I've wrapped them up into a library. We've also included implementations of the recipes from the itertools documentation. Enjoy! Any additions are welcome; just file a pull request.
Please see http://packages.python.org/more-itertools/api.html for the list of routines.