Arduino Forum - Hue-controllable RGB LED lamp
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1207331496
The hardest part was converting HSB into RGB - the equations that I worked on from wikipedia are an absolute nightmare to translate into code (at least for me at this stage). I was about to give up when I saw this link, full of ready-made colour conversion functions: http://www.easyrgb.com/math.php?MATH=M21#text21.