A new iPhone is coming and if you want to smartly get rid of your old iPhone before it gets even older, you would want to sell it off for as much as you can get. If that's too much work, go for perhaps the easiest route: sell your old iPhone back to Apple. They're taking old iPhones with open arms.
Apple is accepting old iPhones as part of its Reuse and Recycle Program and the value you get from Cupertino actually isn't too terrible: an excellent condition iPhone 4S 64GB can fetch $345 while a used and slightly scuffed iPhone 4 16GB will still score you $160. All you have to do is send the iPhone with the power cable and Apple will give you a gift certificate which you can promptly use to buy... your next iPhone. It's like swapping car leases but for phones. [Apple via The Next Web]