Last year, I was stupid enough to think that I needed new (or newish) textbooks from the law school bookstore. Each semester I was spending about $600 on books. This year, I've seen the light: Amazon, eBay, and other websites that save students from wasting their money in college and grad school bookstores. I bought all my books this time for under $250, including shipping.
Yesterday, I also listed some of my old textbooks on Amazon. I've tried to sell old textbooks before, but I always used eBay, which charges you just for listing an item and takes forever to set up a listing. Amazon is my new favorite internet store. It takes maybe 2 minutes to list a book, and they only charge you if your item sells. I listed 6 books yesterday, and by this morning 5 of them had sold. While I may have been able to sell them back to the law school bookstore for $50 (total), I just made $300 overnight.
I highly recommend this to incoming law students.