Mohammed Bah Abba actually invented the fridges in 1995 but they're so simple its definitely worth spreading the news as far as possible.
"You take a smaller pot and put it inside a larger pot. Fill the space
in between them with wet sand, and cover the top with a wet cloth. When
the water evaporates, it pulls the heat out with it, making the inside
cold. It's a natural, cheap, easy-to-make refrigerator."
Thanks to Chris Gupta for passing it on.