I donate them to the library as well. They either add them to circulation, or sell them during their book sale. If you had a massive amount, I could see bringing them to a shop to sell, and then just donating the rest. We never bought very many, so donating was the easiest and quickest way to find them a new home. Still trying to convince my spouse to get rid of about half the ones we still have, since they haven't been watched in years and we could easily get it from the library if the mood struck.