Last semester, I used this search engine developed by this guy I met called carolinaswap.com. Basically you register a user name and create a list of books you have avaliable for sale/barter. Then you search for the books you want with their engine. It searched the user database, used textbooks at Amazon.com and a few other places. It was great and cheap.

I don't think many Professors consider cost efficency in planning their cirriculum. They stink.