You can see the investor returns here: https://btcjam.com/stats

Tips on how to get started
http://blog.btcjam.com/post/75934926878/the-3-rules-of-peer-to-peer-lending-for-investors

Video explaining why BTCJam and how to invest:
https://www.youtube.com/watch?v=p9fvxhVH1pc