Here is a simply brilliant (pun intended) idea that uses recycled plastic bottles to provide home lighting in third world countries. A single bottle installed in the roof can provide the light equivalent to a 60 watt bulb, free for up to 5 years!
Fast Company has a piece highlighting the development of this idea at MIT as part of their “appropriate technologies” initiative. And here is a link to a video that shows how this idea has begun to be adopted in the Philippines where as many as 10,000 of these bulbs are already shining.
Brightens my day just thinking about it!