Planet Bike Super Spot 1 Watt LED Headlight
A 1 watt LED is pretty powerful and bright and more than adequate for lit trails.
It has 4 AA batteries that really last for 30 hours. It's visible from the sides as well. You can buy and install 2 of them on the handlebar for $50.
And don't forget about
Planet Bike Blinky Superflash Tail Light
http://www.nashbar.com/profile.cfm?c...0Planet%20Bike
My general advice: Look only at the lights that have 1 watt LEDs.