Comment Fix bugs. Make something you'd use yourself. (Score 2, Insightful) 283
Is there a bug tracker on this project? Tracking down and fixing bugs will force you to become familiar with the codebase, and hopefully, expose you to code from which you can learn.
Also, find projects that you will use personally on a regular basis--i.e. "scratch your own itch". You'll do better work if the end result is not just some code somewhere, but something that you need and make use of frequently.