Bob Dylan and Johnny Cash did a session in 1969 that was never released in the US. They are very rough, but interesting. While I like Bob Dylan as a songwriter, Johnny Cash cleans him up on singing. Interesting stuff, but you can see it would have needed a ton of work if they were ever going to release it.
1 Million Free and Legal Music Tracks This is a brilliant site for finding new and interesting music. I roam the links and find all kinds of great stuff, all legal and all free.