Your own virtual library
This site looks pretty interesting: http://www.shelfari.com/
Keeping track of books you have read, and books you want to read is a pain.
Having a place to do that, and get recomendations on top of that is great.
Now, if I just found some time to read all these books…
via: http://www.techcrunch.com/2007/01/18/keep-an-eye-on-shelfari/