Jeff,
 
Here are the links that I promised you!!!
 
Jessica
 
Half.com is probably the easiest way to sell a book.  You just hold on to you book until somebody buys it. It is owned by ebay but the format is a little different.  It is not an auction, but just a posting to sell your books.   I haven't sold any book on it but I have bought a few from there.  I think that there is a small fee for listing the book but I'm not sure what.
http://half.ebay.com/
 
Here's a good web site to look for new and used textbooks to buy and SELL
http://www.textbookhound.com/
 
Check out these site about buying and selling textbooks too!
http://www.campusbooks.com/?source=Overture
 
http://www.ecampus.com/