Shelfari 

recently accepted an invite from a friend to join this community. i especially like this site because you can post any number of books in your personal library for free. i originally encoded part of my library to LibraryThing--which is an excellent website, by the way (but you have to pay a membership fee after you've filled up your free 200 titles--and just exported to shelfari. it's just weird that about 30% of my LibraryThing list wasn't recognized by shelfari. just the same, it's an interesting community of book fans.