I run a 2"x4" red light on the back of my rack, with a little red flasher attached to my seatpost. My front light is Planet Bike 5 LED Beamer. Now that I am commuting more, I am thinking about getting something brighter than the Beamer I have.

My big beef is with people who only run flashing lights. I find them difficult to track in the dark. Consequently, my headlight and taillight are steady, with the only flasher on my seatpost.