Very nice Conway's Game of Life sketch for DigiSpark USB development board (or equivalent ATtiny85) and 20 LED (4x5) Charlieplex shield. Easy to assemble, fairly inexpensive, and fun toy.
DigiSpark USB Development Board: http://digistump.com/products/1
DigiSpark 20 LED Sheild: http://digistump.com/products/13
AUTHOR INFO: // I've squashed some of his quirks and introduced all new ones, I'm sure. // https://github.com/pfriedel/TinyLife // heavily inspired by Ben Brandt's TinyChuck5 // http://b2ben.blogspot.com/2011/02/diving-into-microcontrollers-my-tiny.html