Open a serial terminal on your Arduino, and juste write text on it.
Use a damn arduino IDE, or just do :
% PORT=/dev/tty.damnUSBport make upload
if you're using something else than an Arduino Uno, get it from :
% make list
and do (with e.g. an Arduino duemilanove):
% ARDUINO=atmega328 PORT=/dev/tty.damnUSBport make upload
http://github.com/guyzmo/LeLoopOneLineLedDisplay
It's WTFPL ! And as a beerware-compatible license, I wish to add that I prefer good belgian brown beer :)
Patches and improvements are also welcome!
Thanks to my friend Clem who gave me the font I'm using to display on it, and to my friends gric and lekernel who helped me out starting on that one.