Tim
Phase angle control is the easyest way to control the volume of a light
(incandessent) if you need to use flouressent then consider the HF ballast
from phillips they take a 0-10v signal same as many commercial dimers.

A consideration with phase angle control is the ammount of noise radiated and
conducted this needs to be controled with capacitive and inductive filters.

Low voltage lamps were described in a recent mchip seminar using pwm and a
single FET these make a simalar ammount of 'noise' but due to the switching
frequency it is simpler to filter.

Cheers Steve.....