Where do you sell back your textbooks?

I don't recommend selling it back to the bookstore. Your university bookstore tries to make as much on the transaction. You're lucky if you get back 25% on a buyback (and the bookstore might try and sell it used for 75%). My recommendation? Go to the first day of class during the next semester for the same class and offer to sell it to students at the door. You're likely to get at least 50% if not 75% (or more) to sell it directly to a student who will need the same book. Cut out the middleman and everyone (except the university) will benefit!

Some schools bookstores will buy the books back for a lower price. You can also put an ad up somwhere, maybe around the school, for students looking for those books and sell them for a cheaper price than the bookstores and make some money off them.

I sell mine to new students. They save money and you make more than what the school would re-pay for them.