If you are driving on the BQE east to west, just before you reach the bridge over the Gowanus you encounter two billboards one after another: Donate your car! Donate your organs!
"Raphael is here thanks to an organ donor."
Both worthy causes. Just be sure you know what you're signing up for. You don't want to be sitting around some Saturday morning waiting to hand over your car keys, when the guy shows up, takes a look at your midsection, and asks, "Right or left?"