A short time ago I read somewhere (the blogosphere is verily large) about these online bookswap services. So I checked out Paperback Swap and was pleased. Mightily.
It's very very very very cool. You sign up and then post (by ISBN) the books you have (not just paperbacks) that you don't want anymore. If somebody wants one, they request it and the system sends you a book wrapper. You download and print the wrapper, wrap up the book, send it to the person (at your expense) and, when it arrives in good condition, the receiver registers the book online as received. Then you get one credit.
One credit means you get to request one book. So you go into the system and see if someone has a book that you want. If they do, you order it and a few days later, it arrives at your door. You go online and register it as received. If no one has the book, then you put it on your wishlist, and the moment someone posts that book, you get a notification.
When you sign up and post your first books, you get three credits. So far I've gotten four books and sent two. Very happy!
It makes so much sense that it's doomed, doomed! Why hasn't such a thing always existed? There must be a Platonic Ideal of a Paperback Swap existing somewhere in the sky. A thousand years from now, the world will be dominated by the religion of the Pfapeerbukshwop, whose main holiday (coinciding with winter solstice) is ritualized by the exchange of small bundles of tree pulp (trees were a form of plant-life that went extinct in the 22nd century.)