Somebody sent me a link to MediaChest, a site to share books, CDs, DVDs, etc:
Mediachest is a new concept based on social networking and what people own. It is based on the idea that someone in your circle of friends or someone you interact with on a regular basis owns or knows someone who owns items you are interested in borrowing. Mediachest allows you to keep track of your books, CDs, DVDs, and games. Using Mediachest is very easy. Adding items takes no time at all and work is being done everyday to make things easier. You can also include pictures of your collection if you feel like showing off what you own.
This seems like a distant cousin of BookCrossing, without the randomness.