3D Cellular Automata in Minecraft (2011) [video]
youtube.com
youtube.com
It would walk a line, sense 3-tuples of redstone blocks, and apply any 1D Cellular automata you wanted to generate a new row. End of row was auto-detected, where it would advance to the next row and continue, accounting for the larger row, and continue applying the rule in the other direction.
Rule 110 worked just fine, though I usually used Rule 105 just because it looked cool.
I'll have to see if I can still boot up that minecraft instance so I can take some screenshots. Unfortunately, some of the mods (1.6.x era) leaked memory badly, which is why I never really went any further with it.
Also, for using cellular automata to eat your minecraft world, the Grey Goo mod is still the best, as it supports both automata[1] and something a bit higher-order[2]. Just don't use it on a world you care about.
[1] now maintained as the fork "Remain In Motion"
(Or just update to 1.7. Most mods should update seamlessly.)