Improving upon another program?

Hello, I have a question or rather need suggestions. In my class we need to either create a program in regard to a financial aspect. Anything financial, no specific category. The other option is to improve an existing program, does anyone know of any sites that have open source programs that would also have more beginner oriented programs? I've tried a few sites that google pulled up but most of the stuff is way out of my league, lots of GUI related programs.

Any sites that would have beginner open sourced code/programs? Thanks!

I'd search through Google Code, you're bound to find something there.

Create your own ATM simulation seems a reasonably popular request around these parts.