This is an easy way to add light to your bike, so when your riding at night you don't get smoked by a car(If this actually saves your life, take the time to tell me =D). Also putting LED's in anything is fun, so why not?
Step 1: Materials
~LED, the brighter the better
~Battery pack with switch, or other smallish 3-3.6volt power supply
~Drill with 3/16" bit. Use 3/16" for a 5mm LED