@Homer I've made a 2 double LED dimmer as well works very good and can easily be extended with more dimable leds. See my project here

@Session Yes, there are plenty of "certified" dimmers that are controlled by PWM or 0-10V input. However, there are also plenty of "certified" LED drivers that you can also use by connecting the (-) negative side of the DC output to the Arduino ground, and the (-) negative side of your LED to the mosfet output. Certification is for the AC part of the Driver. The great thing about the new LEDS is that you can control the DC side and not worry about controlling the AC. You don't need a triac, you don't need a zero crossing detector, simply switch on and off (PWM) the negative side of the DC part of the light.