Something similar is bookcrossing.com. You read a book, then 'release it in to the wild' by leaving it in a public place with a sticker and unique book-crossin

Something similar is bookcrossing.com. You read a book, then 'release it in to the wild' by leaving it in a public place with a sticker and unique book-crossing ID. Other people can then pick it up and pass it on, leaving a trail online of it's travel across the globe. It can be entirely free, although there is a store where you can order the stickers, and unlock 'pro' features on the website.