Update: I hooked up a dimmer switch to the George map light and it works awesome. Here's a picture of the switch.
http://www.brian894x4.com/images/Exp...erior055xx.JPG
I can't remember the company off the top of my head, but it was mentioned earlier in this thread so I thought I'd give their dimmer switch a try.
I can cut the brightness to about 20-30% of full power and then go up from there to 100% with the dial. Anything less than that and the LED just shuts off, so it doesn't have an infinante dimming ability.
This makes it much nicer when I'm driving and my passenger or I need to use the map light. The map light is SUPER bright and really nice, but when driving its a lot nicer not to be blinded.
I'm not sure how this dimmer affects the circuitry or the longevity of the light, but so far, so good.