Free Time

So I've obtained a bunch of free time. I want to extend my knowledge of C++, Java, and Python. I know the languages, but I think it is time that I learn libraries so that I can actually make stuff.

Also, anybody know any cool open source groups that I can join so that I can actually use my new skills?

As for my background, let's say I am really good at physics and math.

Well, the thing is, I have some free time. I just want to make programming a nice hobby. I won't be using it for income.