WhatShouldIReadNext.com is a site that answers exactly what it asks. Type the title of a favorite book into the search engine and the site generates a list of similar books. Not only is it easy to use, it’s “more than a little bit addictive.”
GoodReads.com is a “social network for book lovers” that’s much like Facebook, except that the communities and conversations you start or join are focused on books you love and books you’re reading.
Bookshelves.tumblr.com is a site that “obsessive-compulsive organizational freaks should probably avoid.” It’s simply a photo archive of books shelved or stacked in libraries, in homes—even outdoors and in bathtubs. Book lovers will lust after most of the collections, but some stacks are so rickety they may prove “uncomfortable to look at.”
Source: Black Book