Booxter, a book collection management program for OS X
Deep Prose Software: Booxter
I like this app, even though I don't really have a use for it personally. I had a similar idea recently, and also thought it would be excellent to support bar-code scanners. If you want to maintain a database of information about your books, this looks pretty slick.
PS: This link and the previous one courtesy Stepwise, the weblog in denial. ;-) Thanks Scott!