Goodreads - See what your friends are reading.
Curlie Directory - Curlie is the largest human-edited directory of the Web.
BookWyrm - Social Reading and Reviewing
Best of the Web Directory - Editors hand-pick every website and blog, making listings consistent, relevant, and unique.
BookAuthority - BookAuthority collects the most recommended books on business, technology and science - as featured on CNN, Inc and Forbes
DMOZ - DMOZ is a multilingual open-content directory of World Wide Web links.