Mark Csele has built a Laser Light Show Controller based on the dsPIC 30F6012 microcontroller. There is a good operational description that could spark some of your own project ideas.

"In a basic light show, a beam from a laser is deflected by two galvanometer scanner heads, each of which moves a mirror to steer the beam in the horizontal and vertical direction independently. Given the high speeds at which these galvos are required to operate, they are quite pricey. As well as the actual galvanometer movements a driver is required which usually has feedback from the sensors. The entire system is usually a PI or PID (proportional-integral-derivative) control loop with the output fed to the galvos and feedback supplied via a capacitive sensor inside the galvo scanners themselves - you can probably appreciate the expense of the scanners owing to the fact that they contain a variable-vane capacitor which changes at most a few pF during rotation. The driver/control-loop usually accepts analog signals: in my case the GSI-Lumonics scanner board employed gives full deflection in one axis with an applied signal varying from -3V to +3V (it is bipolar)."