Have you all heard of Paperback Swap?  You can list you old books, then if someone wants the book you pay for shipping and you get a credit.  Then you use the credit to get another book.  Or you can purchase credits for $3.45 each.  It's a great way to get books at a great discount. 

http://www.paperbackswap.com/index.php

That sounds great! :D Thanks for sharing.

I've not heard of this...thanks Tiffany for sharing!!