LibraryThing is a social cataloging web application for storing and sharing personal library catalogs and book lists.
LibraryThing was developed by Tim Spalding and went live on August 29, 2005. As of September 2009 it has 850,000 users and nearly 44 million books cataloged.
Users (informally known as thingamabrarians, a term coined by contributor RJO) can catalog personal collections, keep reading lists, post book reviews, and chat to other users who have the same books. While it is possible to keep a library catalog private, most people choose to make their catalogs public, which makes it possible to find others with similar tastes. Thingamabrarians can browse the entire database by searching titles, authors, or tags generated by users as they enter books into their libraries.
Everything you want in a website about books. You can catalog your library, chat about books (and just about anything else), enhance the site data, and so much more. LibraryThing has an early reviewer program to connect new books with reviewers, widgets for your blog, statistics and memes to give you more data about your library.....etc...etc....etc... Seriously, best website ever!