Does PyPy work with NLTK?
At least some of NLTK does work with PyPy and there is some performance gain, according to someone on #pypy on freenode. Have you run any tests? Just download PyPy from pypy.org/download.html and instead of "time python yourscript.py data.txt" type "time pypy yourscript.py data.txt".
Does PyPy work with NLTK, and if so, is there an appreciable performance improvement, say for the bayesian classifier? 
While we're at it, do any of the other python environments (shedskin, etc) offer better nlkt performance than cpython?