See, I'm not particularly interested in the plugin part, because I want part of working with other coders for the experience. A plugin would be just another thing done by me on my own in a vacuum with no feedback.

As for open source programs I use on a daily basis and am interested in, they're mostly huge projects in C/C++ (Linux, Chrome, etc etc). Wordpress is the exception, but I haven't came across anything I need them to do that hasn't been covered in some plugin somewhere.

Which is why I asked here, in case there was some interesting project I would be interested in that I have the capability to actually do something useful for.