If you are planning to implement moving message display consider using a PIR sensor. There is no need to waste power if no-one is seeing the message. Jer have built simple moving message display that lights up when people is around.
He used simple PIR sensor, that activates Atmega8 microcontroller which starts displaying messages. It is perfect solution to put it near entrances where people would see some welcome message. Or use project as starting point for more great projects that would include sound, or mechanical movement triggered by PIR sensor.