I checked out the Goodreads, Library Thing, and Shelfari to see if they would be good for our library. It would be good for a public library, but not so much for an academic library. In searching each of them they all had their strengths and weaknesses, but for my personal choice I go with Goodreads.
The books are easy to find and easy to import some of my books to the site. I like the link to Amazon too. It is so simple to use Goodreads. Just put in some titles you have or have read and then see what other books fit within those tags. I found a couple of authors I didn't know about on the first try.
That's all for now.