I take mine back to the dry cleaner. My understanding is they recycle them.
There are some metal artists around JP who might take them. There's also someone who drives around the night before trash day picking up metal (also in JP; maybe other parts of the city as well). Post them on freecycle and see if you have any takers. You'd be surprised.
The cleaner's near me sometimes posts a sign that they need hangers, so Joseph's idea is a great one, too.