Incredibox: Basically build your own beat box. It's friggin awesome.

http://www.stumbleupon.com/su/8kB9yG/9UTgKLea:As8KY1!q/www.incredibox.com/v3

I just spent way to much time fiddling with this fun little web app called Incredibox.  Check it out for yourself!  Build your own beat box.