Choose something you use yourself. From the discussions on the user mailing list/forum you will soon find out what features users are missing. Or take a look at

Choose something you use yourself. From the discussions on the user mailing list/forum you will soon find out what features users are missing. Or take a look at the bug tracker. Many procects have todo lists somewhere in the source tree. The usual way would be to implement a feature you miss. Before contributing, check how the developer team reacted to patches in the past -- there are teams that tend to ignore them. Most often developers will happily help you if you have specific questions about the code. Start with small patches or isolated modules that don't take the core developers too long to review and adapt to their "style". Adhere to the project's coding style.