MIDI Farm
This popular archive contains over 12,000 free MIDI and Karaoke files. There's a local search engine to help you find what you need. All files are "believed to be in the public domain." (i.e. free). Categories include anime, big band, bluegrass, Christian, holiday, classical, contemporary, country, dance, Disney, drum patterns, film, funk, game, Irish, Jazz, pop, ragtime, show tunes, TV, video games and more. There's also a comprehensive selection of MIDI utilities for both Macs and PCs. 

Absolutely Free Mp3s
This flashy site contains free MP3 files, skins, software, and links. File collections are reviewed with positive and negatives. The skins are reviewed with screen shots and given a score out of five. Quite a bit of software is reviewed and scored as well, this site is worth a look. 

Deluxe Mp3 Hits
Get the absolute latest and most popular music in MP3 format totally free. With a number of charts from all over the world, this site is sure to have the hit music you are in search of. One nice feature here is there MP3 search engine that allows you to search thirteen MP3 sites for the song you want.