Arduino Home Light Dimming
DMX512 is widely used for controlling stage lighting. Since it uses EIA-485 the hardware and software should be quite easy to implement on an Arduino with a suitable shield. Here is an Arduino DMX project.

Low-cost DIY remote DMX dimmer controllers are available, here is one which uses an ATmega8515 AVR, a similar device to that used on the Arduino. I'd be inclined to use a much smaller, cheaper controller. The dimmer interface to the lamps, the "power unit", is also described. It's a rather nice project.