The urge to build something was there again, so i ordered this LED-strip from dealextreme.com
Waiting for the LED-strip to arrive I already wrote the software part, it looks like this:
When I click or drag anywhere in the spectrum it sends the RGB values to the arduino.
When the LED-strip arrived I bought some transistors (BUZ11’s, extreme overkill, but hey.. ) and hooked everything up.
End result: