AmazonThing

I'm normally on Amazon.ca, which doesn't have all of the fancy features of Amazon.com, so it's just today that I discovered Amazon's

Your Media Library - http://www.amazon.com/gp/library/

Your Media Library is a secure location to store information about all of your media purchases

It looks a lot like LibraryThing or Delicious Library - you get shelves, you can tag items, you can add items by ISBN, ASIN or UPC.  It supports in particular books, music and videos.