WSJ writes about LibraryThing.com:
Creating a personal catalog is time consuming but also surprisingly easy. After signing up for a free account — only a username and password are required, with no personal information or email necessary — members can enter the ISBN numbers, author names or titles from their books. The LibraryThing search engine, which is connected to Amazon.com, the Library of Congress and 45 other libraries around the world, returns likely matches.
A click adds each book to a personal virtual library, along with the title’s complete card-catalog information and a thumbnail of the cover art, when available. Personal catalogs can be sorted by author or title — or even viewed graphically as a colorful collection of book covers.