I dont want to appear as a lurker mike, however you can to an extent control power and fire at mains zero, its done with large loads in industry, burst firing modules do it, you can fire for a half cycle, then a full cyclle, then a full cycle and a half and so on, it doesnt give you a lot of control, but for large loads that take a lot to change, such as a 10kw heater the system works well and doesnt needs loads of filtering.
As far as the op is concenred however with lamp dimming the way to go about that is as mentioned phase angle control, you'd need an i/p to the micro that tells it the mains just went through zero, then a timer would start creating a trigger o/p when its timed out, the timer would be the opposite of the power level, zero being max power.
Take a look at this:
**broken link removed**