I've a fair amount of competence in python and am learning Django on the job. I've always heard that you can buff both your skills and your resume by working on open source projects, so I'd like to get into some that use python. Unfortunately, I don't know of an easy way to find open source projects by primary language.
Obviously, this applies to more languages than python, so hopefully others can use this once it's answered. [Also, not tagging as python, since the question is general.]