So I finally made a gig-worthy light controller.
Eight independent channels, controlled via a DB9 connector on the side. Used electromechanical relays this time so I couldn't connect hook up the Arduino directly. A single ULN2803 transistor array sinks current from the relays, stepping the arduino logic signals up to 15V. The relays are louder than I expected, but it shouldn't be a problem if music is playing.
Wrote a quick interface for Vixen via the serial port. I used a sample sequence I had seen in a christmas light video a few years ago. I realized I don't have any lamps left in my room, so I had to use whatever I found (a ropelight, a lawnlight and a string of goofy ghost lights).
I'm hoping to do some stuff with the drumkit now that I have the 8 channels.