One advantage the Arduino has over the Netduino is a lot of high power GPIO lines, 13 of them each capable of 40mA which poweres 2 LEDs per IO line fairly brightly, and 6 of these can be run as PWM which make LED's appear go dim or bright.
Armed with a spare Arduino, a little too much time on my hands, a ghost that needed adapting from 110V to work in the UK and a bunch of white LEDs I set about making an Arduino powered Ghost ready for Halloween.
Here's the result (first 12 seconds are dull, hold on in there):
Warning: This video contains some images of bright flashing LEDs, don't watch if you are affected by that!