Throwing another punch at college bookstores, Amazon's released a free iPhone app that lets students check prices, trade in books (for a gift card) and, of course, buy textbooks. It also comes with a six-month membership in Amazon Student, which provides free shipping and discounts on required college accessories -- like snacks.

One interesting part of the program: Not only can you trade in books, you can do the same thing with electronics, video games and DVDs, among other things. It's a whole new way of cleaning out your dorm room. Source: Amazon Get the app here.