Browse the list of Google's Summer Of Code projects (e.g. 2014 list: https://www.google-melange.com/gsoc/projects/list/google/gsoc2014 https://www.google-melang

Browse the list of Google's Summer Of Code projects (e.g. 2014 list: https://www.google-melange.com/gsoc/projects/list/google/gsoc2014 https://www.google-melange.com/gsoc/projects/list/google/gso...), pick the one that interest you the most and contribute to that. Those are all projects that explicitly want someone to help them with something. There's also http://sourceforge.net/p/forge/helpwanted/ http://sourceforge.net/p/forge/helpwanted/ and https://help.github.com/articles/where-can-i-find-open-source-projects-to-work-on https://help.github.com/articles/where-can-i-find-open-sourc... and I'm sure if you Google around, you'll find more lists like that.