I use Serengeti flashlights Sam's Club - Serengeti LED Flashlight - 2pk
from Sam's Club you get 2 for under $30. You can use a couple hose clamps for each flashlight to mount to the handlebar. DealExtreme will sell you some nice conversion clamps for a couple bucks each, there are a few choices, but they take a while to ship from Hong Kong.
The lights are VERY bright, have 2 intensity levels and can adjust size of beam, plus strobe setting. I mount 2 but only turn one on at a time.