A lot of times, students simply need textbooks for one semester.
There's a Web site out called Chegg that will let you "rent" a textbook, rather than buy it. They also promise to plant a tree for every book rented, which is nice and environmentally friendly.
I checked this out quickly for my CIS 106 class.
The bookstore is charging $86.75 for a new textbook and $65.25 used. A lot of that value disappears because most students do not plan on keeping the book, and they will sell it back to the bookstore for somewhere around 10% of the price.
Chegg has the book for $33.26 for a semester rental. Our semester ends a little later, so you can expand it for another 15 days (which would take you through finals) for an additional $4.99. The final cost would be $38.25. They also would pay for your shipping back, giving you a pretty decent savings.
This is a really interesting idea that I really like.