This Credo blog post describes earth-friendly ways to dispose of devices you no longer want.
An excerpt from the post:
ECO-CELL is the group CREDO Mobile works with to recycle cell phones. When CREDO members recycle their phones through ECO-CELL, it determines the phone’s value and sends CREDO the money. CREDO donates 100% of the money it receives from ECO-CELL to nonprofit groups.
The World Computer Exchange is a global education nonprofit that connects youth in developing countries to digital skills and opportunities. They are in need of working equipment.
eBay for Charity lets you sell your used devices (or anything else, actually) and donate part or all of the proceeds to a charity of your choosing.