I joined bookcrossing.com today. I've actually seen the name about for a bit, but this was the first time I've ever really looked at it. I like the concept. Obviously reading is something I think is important and if dropping a book off somewhere has a chance of getting one more person reading, then I'll happily drop off a book or two (or more!).
I started my bookshelf initially with 3 books: Killobyte by Piers Anthony, Magic Casement, and Kushiel's Dart. The first two I've gone ahead and released to the wild - one outside or grocery store and the other on a bus stop bench, but Kushiel's is far too adult to release to the wild like that. I'd be concerned about a youngster getting a hold of it if I just set it free like that. So I've put it up for adoption.
Update:Kushiel's Dart was claimed pretty dang quick! I hope to sending it off to its home soon.