Goodreads - See what your friends are reading.
BookLikes - BookLikes is a free blog platform for book lovers. 100% independent and free.
LibraryThing - A home for your books.
Riffle - Just good books and the readers who love them.
BooksLoom - There are more than half a million books published each year in the US alone.
Shelfari - Discover and share books you love on Goodreads, the world's largest site for readers and book recommendations!