The Internet Archive has a ginormous collection of free, downloadable music in their NetLabels category:
This collection hosts complete, freely downloadable/streamable, often Creative Commons-licensed catalogs of 'virtual record labels'. These 'netlabels' are non-profit, community-built entities dedicated to providing high quality, non-commercial, freely distributable MP3/OGG-format music for online download in a multitude of genres.
There are over 500 sub-collections available here; you can search by mediatype, keyword, collection, etc. A good (free) way to add to your music collection.
NetLabels [Internet Archive]