Warning, this is a techie post...

I just read a post where someone was commentint on light color and dimmers, and he used the term "resistive dimmer". I don't believe I've ever seen a resistive dimmer used for lighting. The older style of dimming (used in theaters and such) was done with a variable transformer, which actually changed the voltage going to the light fixture. Most home dimmers use an SCR or Triac to change the amount of time a light is on. They don't actually vary the voltage at all, it's still 120 VAC going to the bulb, but instead of being the normal sinewave, the voltage becomes more pulsed, with shorter pulses giving dimmer light. That's why the filaments in incandescent bulbs will buzz (or ring) and why most florescent lights will flash. This type of dimmer is actually pretty easy to make -- I made several of them when I was in high school.