CFL bulbs can help you cut quite a bit of energy usage in your home, but you can't measure brightness by looking at wattage levels, like you can with incandescent bulbs. This chart will help you figure out the brightness of CFL bulbs.
Home-centric weblog Apartment Therapy put this chart together to measure wattage equivalents in lumens, which are a measurement of light output (unlike watts, which is actually a unit of power). Some CFL bulbs will put their wattage equivalents on the box, while many don't -- so this chart should help give you a good idea of how bright your new bulb is going to be. Remember, though -- not all light fixtures are suitable for CFL bulbs, so make sure you're using them in safe housings before you buy. Hit the link to read more.
How to Buy the Right CFL: A Cheat Sheet [Apartment Therapy]