While I haven't sold them, I have re-gifted some and donated others. If you do re-gift, don't give it to the person who gave it to you or to anyone who was there when you opened it. And I wouldn't sell, re-gift, or donate any gift that the giver would expect to see you use, wear, etc. Keep it and try to use it around the giver. Don't forget to write thank you cards to everyone who gave you a Christmas present!