UNDATED - If you're trying to get your electric bill down or reduce your carbon footprint, no doubt you've considered using compact fluorescent lights. Consumer Reports, with the assistance of an outside lab, just tested hundreds of compact fluorescent lights, or CFLs.
CFLs have improved dramatically in the last 5 to 10 years. First of all, they've come down in price. And the color that they give is much better. They turn on faster, and they don't hum or flicker or buzz anymore. All the CFLs performed well in the tests. And results show the intensity and color of these lights are now pretty close to what you'll get from a standard incandescent bulb.
As for price, long gone are the days when some CFLs could cost as much as $20. Now they go for somewhere around $2 to $3. Consumer Reports says shop by price, and always get CFLs that are Energy Star-qualified. Worth noting, CFLs should be used in fixtures that stay on for at least 15 minutes at a time, or else you'll shorten the life of the bulb and reduce the energy saving benefits.
As for savings, Consumer Reports says for every CFL you use, you can cut your electric bill by about $5 a year.