Digital signs are everywhere. You see them in airports, malls, department stores and even street corners. Most of them are controlled by expensive proprietary software.
Friends of mine at Mozilla wrote the Corsica Digital Sign Server that they use to drive dozens of screens at Mozilla offices around the world. It’s an elegantly simple design. The individual screens just run the Firefox browser and the Corsica server provides central control with content on each screen customized for the local audience and language.
The Corsica server will run on almost any computer, even a RaspberryPi, and like all Mozilla software it’s free and open source.
I fixed that problem with an article on Instructables.com that shows how to set up Corsica on a RaspberryPI. It’s written for absolute beginners, now anyone can have a digital signage system with dozens of screens running on a server that costs less than $50. RaspberryPis can run Firefox on each of the display screens as well. I doubt there’s a lower cost digital signage system available anywhere.