Having come accross this fantastic website last year, I began experimenting with LED lights, after making a number of halogen bikelights. This is the result of my experimentation:
The casing is built from four 22mm copper end-caps bonded together, three housing the 'U' Bin 3W stars and the fourth to hold a Fatman driver. This is sealed using the top from a bottle of soy sauce. I've added a potentiometer to the fatman to provide stepless flicker-free control of brightness from a decent low beam with 80Hrs runtime to full power (300 lumens +) for 3.5 hours.
The light is powered from a 7.2V 2400maH Li-Ion battery that sits in an inner-tube sarcophagus held in a 5mm neoprene bag. This straps to the frame using a velcro cinch strap
The whole lot weighs 240gms and I eventually hope to add some better connectors to improve watertightness and shorten the potentiometer shaft.
It casts a good spread of light, illuminating the roads and signs for at least 50m. I found the carclo 6deg optics to produce a flood beam but I might investigate replacing one of the lens with a tighter beam lense, possibly a conventional reflector to illuminate the road surface a bit more. Overall, there is plenty of light to ride at >20mph and the lack of weight of the system is a bonus.