My rotating led display project. It has 16 two color leds (red+green) so possible colors are red, green and orange/yellowish (both red and green on at the same time). So vertical resolution is 16 pixels and horizontal depends on the image, the "hello" image is 36 pixels wide.
Read the whole story from my website:
I'm possibly taking this to the Assembly '08 event so look around if you can spot it. Maybe a bit hard in the big hall, but I'll try to get it to display something easily noticeable. :)
Edit: Video clip taken at Assembly '08: