LibraryThing

It is a website with an aim to help users easily catalog their book collection, discover similar books and meet people with similar book tastes. In other words, it’s a world’s largest book club and a web hangout for book maniacs. Webiste boasts over 16 mil. of cataloged books, over 20 mil. tags and over 200K+ book reviews. (You can check numbers these here)

Features

• Catalog, Organize and Share your books with others
• Get recommendations for what to-read(OR not-to-read) next
• Discover people with similar book tastes
• Embed your book list to your blog or profile (ex; Myspace)
• Browse popular books: by most reviewed, by highest rated, by top/lowest authors, by language, by tags, by top taggers, by recently added, by library
• Add favorite users to your watchlist
• For each book view list of similarly tagged books
• RSS feeds for books tagged by specific tag
• Limitations: enter only up-to 200 books for free, as many as you like for $10 (year) or $25 (life).
• and more… Take tour

Visit LibraryThing