How to sell old college books?

I went to a school online and another school. now I am going to a different technical college and i want to sell my old books but this school doesn't need any of these. I about about 16 books and want to get rid of them. What are my other options?How to sell old college books?
I sell the majority of my textbooks on half.com. You can also try donating them the library, or selling on ebay or amazon. I like half.com because they don't charge a listing fee and no time limits. You can put them on and forget about them till they sell!How to sell old college books?
I usually check with barnesandnoble.com. You can enter the isbn numbers, and they'll tell you how much they're willing to offer you for the book. You can choose to either accept or deny. They also provide you with a prepaid shipping label, so all you need to do is run it to the post office. They mail you a check usually within a week. There are many other sites that use auction techniques, but I've found that barnes and noble usually offered me more money. Also, you can use a variation. When barnes and noble won't match what you want, list the others on half.com.