I have heard that if you turn a light on and off frequently you shouldn't use a fluorescent bulb. Is this true of compact fluorescents?
Also, why do fluorescent bulbs buzz? Is there any way to avoid this?
Fluorescent bulbs have two great advantages over their older cousins, incandescent bulbs: they use a lot less energy and they last a lot longer. The caveat on the latter, though, is that turning them on and off frequently will shorten their lives. You'll still get the energy savings, so no downside there, and they'll probably still last longer than an incandescent, but you might not get that optimal 8,000 or 10,000-hour usage (compared to 1,000 or so for an incandescent).
The rule of thumb is that, if a light is likely to be used regularly for less than 15 or 20 minutes at a time (for example, a closet light), it may not make sense from a bulb-life point of view to use fluorescent. Fluorescents do take a "jumpstart" burst of energy for a fraction of a second at startup, but it's not really significant. You will still gain the overall energy savings of 75% or so over incandescent bulbs.
Fluorescent buzz is pretty much an old-school problem. The previous generation of fluorescent bulbs used magnetic ballasts where the newer ones use electronic ballasts. On top of being more energy efficient, the electronic ballasts do not buzz. All Energy Star qualified CFLs use electronic ballasts. And fluorescent bulbs come in much better colors than the old-school ones did. So the excuses to say "I hate fluorescent lighting" are getting harder to come by.
For more information:
You should read "Are there CFLs or other energy-saving lightbulbs that work on a dimmer-regulated light fixture?" also written by architect David Bergman.