Even better! I used a service like this*:
http://www.cash4books.net/ You don't get much per book, but it is convinient to use. You only register your ISBN number and it will tell you how much you get per book. DON'T LOOK AT THE MONEY PER BOOK!! IT IS ONLY PENNIES! But it adds up and you don't have any further work with it. In the end you just pack them up and they will retrieve the box at your home. Next thing you know there is the money on your bank account.
*I live in Germany so I used another service and don't know anything about this company here, it is just an example.