A friend put me onto LibraryThing. It's a site that allows you to input and tag books you own. It's very cool. It has clean interface and you can even tie in with certain local booksellers (as well as the bigger online ones). I haven't tried this yet because none of my local booksellers are one of the supported ones.
Here is my bookshelf. It would be bigger if I hadn't lost some books while moving.