A free, worldwide membership community with the goal of "making the whole world a library." Register the books you read and pass them along - you can follow their travels through their BCID numbers. Set your books free, and find new ones for free, too!
Go to any small, independent bookstore and you are likely to find the most current issue of the Booksense newsletter. Each month, a list of book recommendations is compiled, based on recommendations from independent bookstore employees. There are also specialty pick editions that focus on a specific theme or genre. These books might not all be on the best seller lists, but they are wonderful books nontheless.
Users join a group of 6 and rotate books each month...so you contribute your own book and read 5 others that are sent to you each month. It's pretty cool...and it's free. So far I've read some great books.