Or take it to your provider

This doesn't help if you feel the need to donate the phones directly, but you can always bring the phone to your provider and they will recycle them. I brought a couple of old phones with extra batteries, cables, cases, etc. to a Verizon Wireless store last week. They have recycling bins in the store. I had wiped the data but I did ask and was told data was safe and all parts would be recycled responsibly. I would assume that the other providers do the same.

You can also take them to Best Buy and I think Radio Shack will recycle them too.