there is an online bookstore that sells cheap used books (and some new books). prices range from 3.98 and up (most are 3.98 or 5.98). The shipping is free in the US and about 2 bucks worldwide (which is pretty impressive since books weigh a ton). The proceeds go to fund world literacy and to save books from being thrown in landfills.
they have almost everything you could imagine, including books that are no longer in print. I bought 36 books there for a little over a hundred, so I have already ordered. And I thought maybe you guys would like the site.
Better World Books
betterworld.com