This is a small circuit that demonstrates Redstone repeaters and a circular power flow. Useful for building traps, or for having a shifting floor. Truthfully, its more or less a do nothing, but it can be entertaining to watch when the mobs get stuck in it.
Step 1: Laying Out the Regular Pistons.
You want to set your pistons out in a pinwheel pattern, so that in the center of the four pistons is a 2x2 square block, and the pistons are set so they face like they do in the photo, so the pistons push towards the face of the next one.
Step 2: Laying Out the Circuit.
Now, we build the paths. Each piston gets 5 Redstone and 3 Redstone Repeaters. Starting at one piston, place Redstone in the pattern in the photo, all that really matters is the repeaters are placed 3 in a row and set on the slowest setting( spread all the way apart) for each piston, and there's a full circuit all the way around.
Step 3: Final Step
For the last step, place a block of your choice in the center of the pistons, and a lever at some point around the perimeter of the circuit, touching the Redstone. Flip the lever on, then shut it back off. You should now have a pulse of power going around your circuit cycling the pistons. If you leave the lever on, it will eventually fully power the circuit and nothing will happen, other then locking the pistons out.
If you want it to go faster, play with the intervals of the repeaters. . too fast and it won't work well.