Here's 2 good sources for other midi files:
Funk, soul, jazz (and of course these can be used for anything):
http://www.smashupthestudio.com/I would tell you to only buy these when they are on sale (like right now they are 20% off).
Classical midi files - you can get about 19,000 classical midi files for about $45! Take a Bartok melody and put a funky drum kit behind it and you're on your way to something interesting... lots of material to play with!
http://www.kunstderfuge.com/