Today I stumbled over
BookCrossing. Part book club, part behavioral study, part note-in-a-bottle experience, BookCrossing encourages people to experience what it terms "the karma of literature" by registering books at the site and then depositing them in public places, like coffee shops, airplane seat pockets and park benches.
Has anyone of you actually tried if this really works? Somehow I would feel strange leaving my books behind in the wild...