Ask HN: do you know of any sites similar to pythonchallenge.com?

Programming Praxis has a ton of interesting problems, many from fundamental Computer Science and often with a functional bent.

http://programmingpraxis.com/

Have you come across Project Euler? http://projecteuler.net/

You can try Marathon Matches at http://topcoder.com/tc (SRMs which are, almost, weekly competitions don't allow Python)

You might consider checking out http://notpron.org/notpron/levelone.htm. It doesn't give programming puzzles, but from what I remember it was part of the inspiration behind the python site you mentioned.

http://www.codingbat.com/ has good python challenges. Simple but good.

this one: http://challenge.greplin.com/