Have you considered Google's Summer of Code? https://code.google.com/soc/
We worked on a package management system like APT for Windows, and while it was a bit unrealistic for 3 students in 3 months, I learned more in those 3 months than entire years at college.
Edit: There's also a Ruby Summer of Code in the same respect as the Google one. http://rubysummerofcode.org/
Besides, the projects are pretty open about it. You can approach a project and come up with your own ideas. Not only this makes you more noticeable, it gives you the flexibility to do what you really want.