BigBox

You could easily waste a ton of time on this bad boy. Basically it's a quick flash program where you can setup 7 part acappella song with some defined items. You can mix and match the different percussion, instrumental, beat-box, styles as well as vocals. There are 14 different types of things, and apparently a new version is on the way. It's a really neat music tool that's very entertaining to use.

Check it out here!