I've been working on getting a driver for a Philips Lumileds Luxeon I high powered LED up and running. I tried a few designs with no success before using National's LM3404. I came across a really nice Evaluation Board that was just a bare PCB so I could pick and choose the parts I needed for my specific application and it was only $13 as opposed to the $40 it costs for the full Evaluation Board. I built up the driver board and connected it to an Arduino and used the Dimmer example sketch to PWM the driver's DIM input. This is part of a larger project I have been working on for a high power RGB computer controlled lighting fixture.