This is an awesome site. You sign up and list some books you have but don't need anymore. Other peeps do the same and when you see one you need, just send them a msg and they mail it to you.

This is an awesome site. You sign up and list some books you have but don't need anymore. Other peeps do the same and when you see one you need, just send them a msg and they mail it to you. 
I've been downloading some free e-books too. They have a daily offering of about a half dozen kindle editions in a variety of categories. I've heard it's a great way to save money (lots of money) on text books.
http://booklending.com/