There have been many cobblestone generators, similar in design to this. This uses a basic, one column design with two streams, one lava, one water. The pistons push it up, then to the side, then out, then up again, allowing for more stacks. This design can be further expanded, but this was a bit of a rush job. I plan on expanding this in the future. Will have a world file up soon!!!
Make sure to turn on all the switches in reverse order, 4-3-2-1, read ALL signs, and if u want it to work, don't change the wiring!!