If you want a blinky light, make the blinking light circuit from Bill Bowden's web site: http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm describes. And I made in this instructable : http://www.instructables.com/id/ED42Y0XZ6BEP286Y2B?ALLSTEPS
This can be made to be just a headlight or both a headlight/taillight bike light system.
My NiteRider light was off getting fixed at the factory and I needed something for my daily commute. I have used it in a 45 minute pouring rain commute on the way in to work and it worked like a champ.