I ordered the Minipov kit from adafruit. POV stands for persistence of vision. Basically flashing seperate images fast enough to make them look like motion.

The kit uses 8 red leds. It is pretty simple to build, it only took about 45 minutes to solder together. It took a little more time than that to install all of the software onto my linux box.

Getting the minipov to display a readable image took some work though. Waving the thing as fast as I could would sort of make a readable image. I slowed the blink rate down some and that helped.

Next I tried was putting it on a bike wheel and spinning it around.

That worked a little better. You could pretty much make out the words. I meant to spell my name CHAD, but the letters came out reversed.

In the above picture it looks pretty clear. That is because I set my camera to have a slow shutter speed. With the naked eye it wasn't nearly as easy to read.

Next I put it on top of an electric motor I had laying around.

That worked a lot better.
I powered the motor using an old computer power supply.

(maybe I should have waited until after the rain had stopped)

That produced a pretty readable message. I took some video with my camera. You can see them
You can see video of it here
and here.

The pov spins in a pretty tight diameter. A larger diamter would probably help. The problem was if I increased the diameter, the motor would get out of balance and fall over. I could probaly use some counter balance, but I was lazy.

The real trick is to have the letters flash at about the same point in the rotation. You can see in the video that it looks like the words are rotating slowy. I fiddled with the timing alot to get that small rotation. If the rotation was too fast it was unreadable.