I used a bridge-rectifier followed by a capacitor and then regulator to run LEDs instead of globes on my stolen bike.
Was thinking about doing something better on current model. When i get some bits and pieces together i'll get some info posted.
The gen. is rated at 3W and 6V AC, so can supply 0.5A. So if we can get 12 Volts out we can run 6 Watts of lighting and so forth. But the gens voltage varies with speed so we need some form of regulation, this is done easiest with DC. So the gens output needs to be rectified with a bridge rectifier and smoothed with a capacitor (guessing around 22000uF will do).
Now we measure the capacitor's voltage at the slowest speed we want full lighting (maybe just pedallin). Multiply this by 0.5 and that's how much power u can supply.
Now choose a front light or reto-fit some LEDs of about 90-95% of your total calculated supply power and source & adjust a DC-DC converter to match the voltages of the supply to the lighting.
I haven't actually tried the dc to dc converter, but hope to in the future. Last time I used a linear (3 terminal) regulator (can't remember the voltages) with heat sink, but i think i'm due for a more up to date solution.
Also, the wiring after the rectifier can lo longer be earthed to the frame. A 2 wire pair MUST be used.
Looking at generators and headlights ATM and have a couple 3W 11V LEDs (ebay, actually measured 11v to be too high, won't last), so i can get this project started, but it won't be really soon.
The remaining 5 to 10% is for the back light, more on this in the future...