According to Wikipedia, the free encyclopedia, librarything.com is “a social cataloging web application for storing and sharing personal library catalogs and book lists.”
I recently joined as a lifetime member. I think this website is very useful and will be around for some time to come. You can find my listing here:
http://www.librarything.com/profile/AmeliaPainter
On the site you can keep reading lists, post book reviews, and chat to other users who have the same books. The site makes it is possible to keep a library catalog private, but most users choose to make their catalogs public, which makes it possible to find others with similar reading tastes.