My daughter isn't as 'net savvy as I am, so I researched the best deals on her college textbooks for her.  There are a lot of sites where you can get used books, but in her case it turned out that half.com had the best deals on her books.  Most of the textbooks cost less than half price, and she was able to rent a couple for four months for about a third of the retail price. We thought we were being smart the first year by ordering the textbooks as soon as the list was available through the college bookstore and using the "used if available" option, but she had to wait until a few days before classes started to get the books and not one was available used.  When I was in college, there was a bulletin board where you could post ads to buy and sell your textbooks, but she was unable to find anything similar at her school.