I heard about goodreads.com on one of my author lists and thought people might be interested in it. This is more for readers, though there is a group of Goodreads Librarians with 62 members. Not all of the site is accessible unless you have an account and log in, but I thought it was worth investigating.
This site uses Amazon to locate books readers want to enter, but information can also be entered manually. You create your own bookshelves and you can add your books to your blog, like I did with Library Thing, and you can import/export your books to a spreadsheet, which sounds like a great idea to me!