Delicious Library can quickly catalog all of your books and DVDs by scanning the barcodes using your iSight. It automatically downloads all the information (director, cover art, etc.). It can suggest similar items. You can automatically buy and sell your stuff on Amazon (not sure how useful the buy feature is). If you sell books or DVDs on Amazon, this is a must have. You can also keep track of who borrowed your items. I don't think it's worth $40 to me, but if it supported other services besides Amazon and had some blogging features, I might be game.