^^^^ Another BF member, probably in the Show Your Commuter thread, had a Coleman hiking headlamp zip-tied to the front of the stem for a really clean installation. It looked like it was built into the stem's faceplate. Cannondale had (has?) a stem with integrated battery & headlight, too.

I recently picked up a Light & Motion Vis360 helmet light that I think is pretty cool.
http://www.bikelights.com/vis360.html
http://www.bikeforums.net/showthread...360-helmet-rig