I didn't know where to post this, so I am doing it here.  I just found a cool new site where you can do a search for a book to find where you can buy it the cheapest.  They give you a list of new books and used books and the price quoted includes shipping.  They don't include the Book Depository in their search list.  They are by far the cheapest place to buy new paperback books because their price is usually less than Amazon and the others and they don't charge for shipping.  With Amazon now charging 3.99 for shipping, that is a huge savings.

http://www.bookfinder.com/