Book Crossing

Ok, so I know I have a few fellow bibliomaniacs out there in blog land! Has anyone heard about book crossing?! You can print or order these cute labels, then you stick them in a book and "set it free!" You can give them to a stranger or leave them in a fun place. Then you watch the progress online. How fun is that?! Plus a great way to save some trees and make someone's day. (I would be ecstatic if I found a free book!!) Who wants to sign up?! (ps: its free!)