I realize I'm geeking out here, but this is really cool: Library Thing allows you to enter in the books in your library and export the cataloging data so you can put your home library in order. (it makes things easier to find...really!) You can also get book recommendations based on your own collection, and from what I understand, it's much more relevant and involved than Amazon's "based on your past purchases" BS where they try to sell you more books. I swear, I bought ONE f*&$ing sewing book back in 2002 and they haven't let me forget it..
Anyway, the first 200 books are free, but you can also subscribe for $10 a year and enter as many books as you want. Love it.