We Read!

Another one:

http://weread.com/ (also has a Facebook app - so does GoodReads!)

Book Related Websites

http://www.librarything.com/
http://www.goodreads.com/
http://www.anobii.com/
http://www.dailylit.com/
http://www.search-pdf-books.com/
http://www.readernaut.com/
http://www.bookglutton.com/
http://www.bookjetty.com/
http://www.booktagger.com/
http://www.booksprouts.com/
http://www.readingtrails.com/

The Army of One

Check out the Book Army website.