LibraryThing is a website which allows people to do the following: keep track of what books they own/want to read/are reading, save reading lists, review other books, add a book to a wishlist, and chat with other readers. If you are adding your collection, you have the option of automatically adding a book and the correct edition for it if it is already in the system, or manually adding it yourself. As of Fall 2009, it had almost 45 million items already added.
Some cool things that it does:
1. Social tagging (tag your book “urban fantasy”, and then when someone searches for urban fantasy, that book will be found). You can also search by tags for books yourself.
2. Add book covers, descriptions, or review for your book
3. Add a profile page so others can connect to you. Include as much or as little information as you like (favorite author, favorite bookstore) and as your collection grows, view statistics about it.
4. Find out what author readings, signings, and discussions are going on in your area with LibraryThing local.
5. Get free books if you join “Early Reviewers” — you get a free copy of a book in exchange for you reviewing it.
6. Find other books based on ones you already like.
7. Find people with book collections that most match your tastes.
8. Add a LibraryThing widget to your blog, or access your library from your cellphone with the mobile version of LibraryThing.
You have the option to add 200 books for free. After that, you can join for either $10/yr or $25 for life.