I was just gonna mention Half Price Books ^. Good store if you can find one local though, ive been to 2 in Pittsburgh and they were great, too bad they arent closer to Philly. Not sure how the website is, ive ordered some used DVDs but if their book prices online match their in store prices it should be good. Truthfully if you really want cheap books keep an eye out for local places (library, or clearance sections of bookstores) cause unless its free, shipping usually kills the deal. Also Half.com aint bad, havent used it in a while but remember picking up some good stuff from there before.