I love this RGB POV in a tube created by rucalgary.
There are 64 RGB LEDs spinning around on an aluminum frame, spun by a motor picked up at Princess Auto for $20.
I control everything via an ATMEGA1284p microcontroller, as it was one of the only micros that had the memory space I needed for images.
I hope to get some more color out of the system by PWMing the color output, but we will have to see that later. Right now I am displaying images just by changing the source code, but I hope to get wireless updates working over Zigbee or Bluetooth.