Rolex Awards Winner Mohammed Bah Abba developed a non-electric fridge.
BoingBoing reports that
"Mohammed Bah Abba of Nigeria won a Rolex award for his "pot-in-pot refrigerator. It consists of a smaller clay pot inside a larger clay pot. The gap is filled with damp sand. As the sand water evaporates, the inner pot cools. Food that used to spoil in a few days now stays fresh for weeks. Second-order effects are already being noticed -- for one thing, girls who had to skip school to sell food at markets can now attend classes."
More at WorldChangers
Update: These guys are 4 years late in reporting. Our trusty folks at Scientific American covered this in 2000. Their Science and the Citizen section is great.