The Daily Green recently did a story about Green Lighting about changing regular bulbs to CFL. While I am in the mode of going from CFL to LED I do recommend this story. As it reports:
This one is a no-brainer: Swap your old incandescent bulbs for compact fluorescents (CFLs). Each bulb may cost a little more (between $2 and $7), but a compact fluorescent will pay for itself in mere months and prevent 450 pounds of power-plant emissions over the bulb’s lifetime.
If every U.S. household replaced just one incandescent bulb with a compact fluorescent light bulb, the amount of energy saved could light 2.5 million homes for a year.