LibraryThing

I've actually used LibraryThing before this and have already cataloged some of the books I have read.
It's a useful site for personal use, but for professional use I think that Goodreads is actually better. You have unlimited cataloging space and the social networking aspect lets you find even more books on a topic that customers might like.
But LibraryThing is still nice, especially since it uses the Library of Congress catalog.
Here's my LibraryThing account.
There you go.
Can we get the deadline extended, please?