BookTagger

BookTagger is a new Australian based book tagging community. From what I can gather it's a little bit like LibraryThing, but with more functionality and more of a community feel. Best of all, it's free! From the site:

Each BookTagger profile is a graphical representation of your physical bookshelf on the internet. The bookshelf can then be shared with friends, family and others searching for the next good read. We hope you'll congregate into book clubs and share reading experiences. Or maybe you'll catalogue all your books and track to whom they've been lent.

http://www.booktagger.com/