I have two passions in life: technology and books. I can't figure out how I didn't know about Bookpedia until yesterday when I stumbled across it. Sure, Delicious Library is the big name in Mac personal media management, but Bookpedia only costs $18 bucks and it pulls info from libraries as well as Amazon (cool!).
It has the iSight UPC scanning, the shelf metaphor, and the lending tracking features, as well as an iPod and HTML exporter. Check it out if you're as much of a book lover as I am.
My one gripe about all of these book cataloging programs is that they are good for tracking what you own, but I really would rather track what I have read. Maybe that's just me though.