http://www.benettonplay.com/toys/orbit/index.phpThis flash game is really addicting in my opinion. If you choose the right sound choices, you can come up with a pretty catchy beat.
If you are too lazy to read directions. press 1-8 on your keyboard, not the number pad. The sounds come in layers of orbits, it spins, and it's kind of hard to explain.
Try it out. You can save your music and post links here. Try some creative sounds.