A Multifunction Led Display is the easiest way to create your own information system display. This display is a kind of colored LEDs controller through the parallel port using a very, really very easy scheme. The software is a Perl script under GNU(GLP) license and works only under GNU with Linux. This version display 3 system views modes: a Binary Clock (Only for Geeks), a Memory Status Bar and HDD Status Bar, the script have a auto mode to change the system views (10 seconds Binary Clock, 4 seconds Memory Status Bar and 4 seconds HDD Status Bar). Link.
HOW TO – Build a Binary LED Clock