Peer 2 Peer Lending?
I did it back in 2009, but pulled my money out due to concerns regarding the SEC and Prosper's general business practices. It was enough to make me sell all my loans and get out.
PropserForum.com used to be a great resource, but it looks like it got shot down. I had other sites, but I don't have any of those links.
I just checked my account, and I still have $15 in there. Now to figure out how to get that out :)