www.urshelf.com
UR Shelf was created by a few Pi Kappa Phi brothers at NJIT in Newark, NJ......(friends of mine...have to give them a little plug)
What's nice is that it finds books on your campus, so you don't have to pay shipping costs, you can just meet up with the person at your student center or something. If the book isn't available, UrShelf automatically searches other schools, and Amazon.com results.
check it out!
www.urshelf.com!!