A few days ago the BBC reported about a program in the Philippines is bringing indoor lighting to some of the country's poorest residents. The program, Isang Litrong Liwanag (A Liter of Light), installs water-filled soda bottles through a cutout in a roof. Chlorine is added to the water to prevent clouding, and the bottle is sealed to prevent a leaking roof. Once it's all done the refracted light is powerful enough to brighten up a home.
Here is a video about the Liter of Light water bottle program:
It's a great (re)use of an item that would otherwise make its way to a landfill, or possibly be recycled. Instead, this common (and inexpensive) household item is literally brightening up people's lives.