We have created a LED control library that allows you to easily manage multiple LEDs of different kinds (regular, RGB, variable color temperature).
You can fade them to a desired value and set the time it should take to do it. You can control intensity, but also parameters like hue and saturation for RGB leds or color temperature for cct leds. The parameters can also be animated independant of eachother (e.g. you may couple one sensor to the led's intensity and another to control the hue).
The library can directly write values to the arduino pins, but also allows you to use the values to actuate DMX controllers, shift registers or any other controller you might want to use =]
If you have a project using LEDs or other light sources, we warmly invite you to give it a try!
The library can be downloaded from http://led-library.googlecode.com
Documentation can be found at http://lithne.id.tue.nl/docs/LED/annotated.html
If you have any suggestions, requests or feedback; please let us know!