ArsTechnica this morning that uses a bag of rocks or sand and gravity to power a nice little LED light making it perfect for camping or even backcountry use.
The Gravity Light is a crowd funded project and has already met it’s goal. But, if you’re interested in getting one you can pay $60 to send one to a village in Africa and receive one yourself. More information on the light and how you can potentially get one is available here: http://www.indiegogo.com/projects/282006.