The FreeCycle Network keeps track of local free-exchange groups whose goal is to keep your used stuff out of the landfills. You can get rid of your unsed stuff and get some more stuff that you might not use! Not a bad deal if you ask me.
I came across a reference to BookMooch. It’s a book-bartering system that enables you to give away your unused books for points and then “mooch” a book from someone else. This is defiantly worth a look.