It is called www.swaptree.com. Swaptree is web service where one can exchange books, CDs, DVDs, and video games. Each user creates a unique account that manages two lists a have list for books one owns that they want to trade, and a wants list for books they would like to receive in trade. When a trade is initiated (it can be two or three way) it is approved by all parties involved. Once that happens the address the item you are sending is given, and you ship the item for about two to three dollars using media mail. When the item is received you rate the user that sent you the item on promptness, conditions, etc. I have only had three negative experiences with two damaged items, and one item I sent that got lost in the mail that has not been found to this day. It is a great way to get rid of books that I don't want anymore for books that I really really want that are not circulating in the library system. The trick is to have double the amount of items on your want list than on your have list. Everyone should check out the website and happy trading!