Permutator
You want to see a decent example of the power of recursion? Check out the source of my letter permutation project I (who has a degree in Mathematics and Computer Science) wrote to try to beat my mother (who has a degree in English) at Words With Friends™.
There's obviously a ton of room for improvement in the project, but hopefully if time permits, I'll have time to improve upon the project as well as blog about design decisions.
Remember: It's not cheating if you wrote it.