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:

Processing sketch

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:
Orange!
Blue!
The transistors