A very interesting project has been funded on Kickstarter:
Meet LEDgoes. It’s the simplest, most versatile, least expensive LED Matrix Display system that exists today, with useful features for all experience levels with electronics. And the software & hardware will be Open Sourced upon successful funding!
You can stack or arrange up to 64 Displayboards together in a single system in any way that you like. Each Displayboard is 1.5 x 2 inches, 5×7 LEDs, and Two Color (can be combined for 3 colors!). *Final Production Boards will have ceramic oscillators for the ATmegas
