Dive into Python has several chapters on test driven development, refactoring, and performance tuning.

I'd also read some of the best books in general development if you haven't already: http://www.codinghorror.com/blog/2004/02/recommended-reading... Also learn about the SDLC. Applies to every language.

Next, dig deep into the source of a large well-maintained projects such as Django or perhaps pygame. Learn mercurial, and start contributing via bitbucket, github, etc.

Find the right project and you should get valuable feedback for your efforts. ;)