Lots of them. Sympathetic resonance is one neat thing about them. Also, if you care to find yourself an old TV, you'll see that the first remote controls used a tuning fork for ultrasonic transmission. (If you get the right kind, you can drive a dog nuts with it.
It probably can't. I didn't realize that such was a requirement for your project. It was merely an example of a practical use for the things. If you're looking for an application for tuning forks that has some social value, I'm afraid that I'm right up a tree on that one. I can't think of anything that they can do that can't be better done some other way.
I have no shortage of ideas, but it should be something that you personally have an interest in. You'll do a better job because it'll be fun instead of just an assignment. What are your hobbies? Anything that you like to do has a basis in some branch of science, from kite flying to bowling to billiards to archery. Even building models involves the chemistry of adhesives and paints, and reading comic books brings up all sorts of possibilities for experimenting to see why someone can't do something like fly or spontaneously combust.