I understand the concept of a singel 8x8 matrix and could probably make one if I had that many led's :P The problem that I would be unsure of would be daisy-chaining all 30 of them. I just figured out that the cost of a single MAX7219 is about 5.50 which already puts the project at 165$ for the drivers and about 60$ for the 8x8's. Unless I can find an 8x8 that is longer than 2 inches I'm stuck with about 30 of them. I need to span about 6~7 feet. Do you think there might be a way to use shift registers? Or possibly another type of chip?
The MAX7219 chip is what's designed for this job. Keep in mind you need a resistor for each LED and in the matrix form, keeping the current to each one constant can be a major headache. The MAX7219 handles this for you.
You could use shift registers, 2 on each matrix for the anodes and cathodes, but the outputs couldn't power the LEDs, so you'd also need 16 transistors per matrix. You'd also have to manually scan each maxtrix in software; manually doing the multiplexing. There is no way the Arduino comes close to the computing power you'd need for that.
As I said right from the start, this will be an expensive project, more expensive than a commercial scrolling sign.