for code reviews you can use http://codereview.stackexchange.com

and for python code review and feedback, try http://reddit.com/r/learnpython/ , it's a great subreddit with lots of helpful senior members.

Apart from the links the other commenters mentioned, there is IRC as well. I don't go there too often, but I came here with some "abstract" questions and I was well received - the last time I went, I asked in #python on freenode the most "pythonic" way to do something.

reddit's language-specific subreddits are a good casual place to start (although they can be surprisingly sparse)