I always advocate donating the phones to victims of domestic violence, if possible. Also many places, like Target, have bins at the front of the stores where you can deposit your used cell phone equipment, as well as electronic items like iPads or mp3 players.
Since most cell phones that are not activated will still call 911 (in the USA), giving such a phone to a person who has been a victim of domestic violence could save a life.
You can probably call your local domestic violence shelter to ask if they have such a program available. If they don’t, they probably can direct you to such a program.