Public Domain Music Library
"DeweyMusic is a new interface for Archive.org's wonderful public domain music library. You can listen to, download, remix, and share anything you see on this site legally and for free."
You can browse the collection (http://deweymusic.org/#browse.php) using a variety of categories (Bulgarian, Dark Electro, Dixieland, Soundscapes, etc.). This is a very eclectic repository.