Scott Carson of An Examined Life points out one of the coolest things I have seen in a long time. LibraryThing will allow you to catalog your thousands of volumes with ease. If you have more than 200 books (and don't most sentient beings?) you'll have to cough up $10 for a lifetime membership, but hey, it'd be worth it, right?
Not like I don't have a lot of other things to do than catalog my library at the moment, but things this cool deserve to be used.