Amazon has quite a lot of free stuff - some of it quite good. The only problem is that they seem to have removed the ability to actually browse for it - you can search, but there is no master list like there used to be.
Another source of free stuff - and/or new and unknown bands is Independent Artists:
http://independentartistscompany.com/Another neat source - an audio blog featured in the Boston Globe back in August:
http://rbally.net/He posted a wonderful Specials concert from 1980 that I snagged a while back.
But now I read that he's packing it in because he's too busy to keep the site going...
- so visit while you still can!