I always try too sell my textbooks online, and then I try to sell them back to some local bookstores if they don't sell online. When no one wants them, they tell me they can recycle them for me, and at that point I just donate them to goodwill.
I haven't tried, but you could see if some bookstores have any books they are going to recycle and see if you can have them. If not that, then the next to free option would be buying old versions of textbooks. There are tons of old edition books being sold on Half.com and Amazon for less than a buck, plus 3.99 for media mail shipping.
To expand on burroughs' point, my grad school also has an open computer network. At my undergrad, students are naive and either forget or don't know to log out when they're finished. You can stake out the libraries and computer labs and borrow someone's credentials. If they come back, just play dumb and say you didn't realize someone else was using it.
