Swap a paperback, or a CD, or a DVD

In efforts to figure out the best way to "pass on" this pile of old books we have, I stumbled upon these swapping sites.

I've just signed up, so can't vouch for them yet, but I'm excited.

For paperbacks it's http://www.paperbackswap.com
For CD's it's http://www.swapacd.com
For DVD's it's http://www.swapadvd.com

The idea is that you list books that you have, send them those that request them, and then you get 1 credit to request someone's book.
Seems like a great idea, saves money, and recycle's the books!