This is the third revision of my bike generator project, the first two can be found here http://www.instructables.com/id/Bike-Generator/ and here http://www.instructables.com/id/BikeGen/ I would strongly recommend that if you plan on building this USB Bike Generator you at least look over how these past to versions went together.
This third rendition of my bike generator project came about after reading some of the comments made about my previous methods. Specifically, one comment from member ac-dc stated that my decision to use a linear regulator to go from 30 volts from the generator to 3 volts to power the light was at best 10% efficient. Now since one of the interests I've had listed on my profile since I joined this site has been efficiency I decided to read the rest of his comment after wiping the tears from my eyes. Ac-dc suggested that buck switching regulator would be better suited for a bike generator like mine. I had no idea what a switching regulator was so I started to do some research and found out that ac-dc was right and that I could significantly increase the efficiency of the electronics I was using.
In my searching for switching regulators I came across this reference from Dimension Engineering, http://www.dimensionengineering.com/switchingregulators.htm. They offer a good explanation of the switching regulators and even sell them.