BeeMP3.com

Music search engine for locating mp3 downloads. Beemp3 doesn't actually host mp3 files, but you can search for songs and it provides links to places where the mp3 can be downloaded.
Beemp3.com claims that their music search is for fact-finding only, and as they don't actually host any illegal mp3's for download they are able to skirt around the legalities - for the time being at least.