The latest addition to shopping & trading online is Swaptree, a site which lets users trade books, videos, music and games peer to peer.
You simply log on and create a list of things you're looking to trade and a list of items you'd like to trade for. Swaptree reviews your lists and sets up the trades for you, the idea being that you're willing to trade anything on your 'trade' list for anything on your 'want' list.
It doesn't cost you anything to trade so it looks like their business model depends on advertiser revenue rather than any user generated revenue.
They're in the midst of beta testing and are set to launch 4th July to the public.
Check it out :: swaptree