LibraryThing is sort of like flickr for books. You can enter in titles and it will search the Library of Congress and Amazon for matching information to allow you to build you library without having to manually enter in all of the fiddly little details.
What would be really impressive is if something which allows you to easily scan bar codes for books (like Delicious Library) would also allow you to export to LibraryThing, the upfront input ramp-up for LibraryThing would be greatly eased.