Web application LibraryThing lets you catalog all the books you own and use tags to organize your collection.
Add book titles by entering a title and viewing search results from
the Library of Congress or Amazon. LibraryThing adds the book's card to
your catalog with ISBN, publisher, year and an image of the book cover.
You have space to add a book summary, tags, your comments and a review.
See what other users also have each book in their library and what
they've tagged it. LibraryThing is an impressive cataloging app that
feels like del.icio.us for books.