If you don't need it anymore, just sell it. I usually sell my old devices to help with 'financing' the new one hehe. As to what price, it's up to the market. Just browse for ads selling the same model IN YOUR CITY and get your price range there (even if in pristine condition, if you sell this for 50 bucks more than what others are offering in the same area, chances are it'll never sell).
You could also try to sell it to repair shops as they could use the parts.
Oh, and very important. Check what the price is for a NEW phone for this model. The same as the old example applies; if you sell this used unit for 25 bucks less than what could get you a new one, chances are people are going to go for the new phone.