Goodreads - See what your friends are reading.
X (Twitter) - Connect with your friends and other fascinating people. Get in-the-moment updates on the things that interest you. And watch events unfold, in real time, from every angle.
BookWyrm - Social Reading and Reviewing
Chaino - The social network where you connect with people, on your term.
BookAuthority - BookAuthority collects the most recommended books on business, technology and science - as featured on CNN, Inc and Forbes
PostedIn - A dynamic content marketplace