I like the way that Last.fm takes what music I listen to and recommends music of a similar genre that I haven't listened to before (or not very often).
I have discovered some good music this way. I would like to enter the books I am reading at the moment and find other books based on the books I read.
I don't want to make "friends" with people to find books that way like some sites seem to do. (Goodreads.com etc)