I use one light mounted on the rack, and I have a Blackburn flea, set to steady, that I mount higher, usually on the upper part of my Camelbak when I am using one, otherwise hanging off the seat. The times I have commuted in heavy traffic, I've added another blinky on top of my rack trunk.

400 lumen Cygolite up front and a 200 lumen on the helmet when commuting.

For side visibility, I have a flashing light on the fork, which lights up the spokes, and some of the high visibility yellow trouser bands wrapped in a few spots around my frame. A few other assorted bits of reflective bits as well.