I'm doing it so you should too!

http://www.paperbackswap.com
swap books for free! ok, you have to pay postage but you get a credit for every book you mail out. one book equals one credit. simple huh? start by listing 9 and get 3 free credits. plus you can print media mail postage right from the site. it really couldn't be any easier. the only problem, more people need to participate. especially if your going to list homeschool books! so come and play!