BookLikes - BookLikes is a free blog platform for book lovers. 100% independent and free.
Goodreads - See what your friends are reading.
LibraryThing - A home for your books.
aNobii - aNobii is a social network for listing books, sharing insights, and meeting people.
Kooba - An interactive graph for finding new books
Riffle - Just good books and the readers who love them.