Apple offers a in which you can get credit in the form of an Apple gift card in exchange for your "gently used" smartphone. Wireless carriers have their own programs as well. lets you get an online appraisal on your current phone; the company will pay you that value in the form of a Verizon gift card. AT&T, meanwhile, has its own program--that company asks you to bring your old phone to one of its stores.

We go into greater detail on elsewhere on Macworld.com.