Here's a demo of the Junkyard Jumbotron, created by Rick Borovoy at MIT's Center for Future Civic Media. It's a cool app to allow you to gang up multiple screens (phones, tablets, flat panels), running any OS, and turn them into a single, joined display. It's very clever: you arrange the screens as desired and then display a web-page with a QR code on each of them; snap a picture and send it back to the server and the server takes any image you feed it and splits it across the screens. No client-side software needed, apart from a browser.
(Thanks, Akwhitacre, via Submitterator!)