I am glad so many are heeding my humble advice.
Original post here.
Buy a single fluorescent lightbulb and put in the light that you use the most or leave on the longest in your house.
CFL bulbs also provide a benefit to the environment based on their energy savings over a regular incandescent light bulb. According to the U.S. government's Energy Star website, if every household in the United States replaced just one incandescent bulb with a CFL bulb, it would have an environmental impact equivalent to removing one million cars from the American roads. 
This is this week's challenge. Check back soon for next week's.
(sub challenge: tell one person about this blog)