Additional recipes for itertools documentation (widespread functions in other programming languages):
* drop
* split-at
* split-by

Added:
* takelast
* droplast

Updated patch with:
* fix error in islice function name
* made n=None default second argument for consume(iterator, n=None) cause it provides specific behavior when n is None which can be assumed as default for function

How are popular the proposed recipes? Not every possible combination of functions is worth to mention in the documentation.

It's hard to evaluate how popular given recipes, but:
* drop is opposite to take, so it's as popular as take
* the same situation with splitat, splitby - it's one case of partition that's hard to write each time with enumerator (partition is already in documentation)
* takelast, droplast was added cause itertools.islice doesn't support negative indices (which is ok). both functions have not obvious implementation - I'm sure that recipes will be good example for users how to work with iterators even if concrete functions aren't so widely-spreaded

I will add drop() to the recipes and possibly take_last() which I would rename add tail().

Sorry, I don't have interest in the others.  I don't find them instructive or very useful.

New changeset 2781fb146f4a by Raymond Hettinger in branch 'default':
Issue 16774:  Add a new itertools recipe (suggested by Alexey Kachayev).
http://hg.python.org/cpython/rev/2781fb146f4a

In the end, I decided to add a variant of take_last().

Thank you for the suggestion.