Seeqpod looks like a really good free music search engine

SeeqPod Music beta, Playable Search (tm)

Seeqpod is a music search engine that scours the web for mp3's hosted by various sites, embedded in articles, linked to in blogs, etc.  It's at its at its core a vertical search engine for the web, purely focused on music.   Built around the search engine, though, is a fully functioning media center - you can play the mp3's, make playlists, save files, and more.  And if you follow the URL's, you can download the mp3's direct from the sources.  In a few random search tests, I found all of the songs I was looking for - this one seems like a great resource for free music mp3 files on the web!