I've created an exciting video walls package running on the Raspberry Pi. You can create a video wall consisting of freely arranged screens in seconds. The screens don't even have to be planar. Just rotate and place them as you like. Configuration is as simple as creating a picture of your screens once you've physically set them up. The rest is completely automatic: You don't have to configure screen resolutions, orientation, size or anything else really. You just have to take a picture. It can't get easier. Here's a video of me demonstrating this feature:
The Pis all run a bleeding edge release of info-beamer hosted. The full package will be available soon if you want to try it out. Happy to answer questions about it.