Good luck with your project, I hope you find a good circuit. I do wonder how you propose to submit a circuit as part of your project when you don't have any idea of how it works or the theory behind the chosen component values, but I guess the real goal of the semester project was to design your own circuit, right?
If I were you I'd trawl through the projects that Gayan has pointed you to for ideas but, once you've decided what you'd like to do, have a go at designing it yourself. You won't learn about Electronics any other way, that's for sure.
Brian