DasBlinkenLights presents a screen full of blinking lights, reminescent of the computers we all see on television and in movies. You can set their color, size, density (roughly how many are on at the same time), and shape (circle or square).
JACKONMACUPDATE Reminds me of the old OS 7-9 screen saver "Lost in Space" which duplicated the intro to that old '60s show with colored circles and squares appearing and disappearing. You could adjust the size and whether you wanted the colors to be random or set. (Version 3.1.0)