CFLs

http://blogs.nationalgeographic.com/blogs/news/chiefeditor/2008/10/cfls-could-cut-world-energy-fo.html

http://blogs.nationalgeographic.com/blogs/news/chiefeditor/2008/12/lighting-revolution.html

http://www.thegreenguide.com/buying-guide/green-energy-efficient-lightbulbs