Not all great design-for-development is high tech. Dawn's post about the Pot-in-Pot cooling system, The Un-Electric Fridge, profiles an amazing example of a technology that's making people's life better with no working parts.
Mohammed Bah Abba's Pot-in-Pot is one of my favourite design innovations ever. Without electrical refrigeration, until now Northern Nigeria's poor agricultural population has had no access to food preservation: "The device owes its cooling powers to a simple law of thermodynamics. When moisture comes into contact with dry air, it evaporates, causing an immediate drop in temperature. When the water in the sand between the two pots evaporates, the inner pot is kept cool, preserving the goods inside."