I just came across http://www.youtube.com/watch?feature=player_embedded&v=xP5-iIeKXE8 , which is an implementation of Conway's Game of Life in ... Conway's Game of Life.
I think it is possible to do this in theory because the Game of Life is Turing complete, but how is it implemented in this case?
jwz has a recent blog entry that talks about this construction: Turtles, all the way down. Or gliders. Or glider turtles. This quote about the "Outer Totalistic Cellular Automata Meta-Pixel" pretty much says it all, in terms that I certainly don't understand:
The rule is encoded in two columns, each of nine eaters, where one column corresponds to the 'Birth' rule and the other corresponds to 'Survival'. The nine eaters correspond to the nine different quantities of on cells (0 through 8). The presence or absence of the eater indicates whether the cell should be on in the next meta-generation. The state of the eater is read by the collision of two antiparallel LWSSes, which radiates two antiparallel gliders (not unlike an electron-positron reaction in a PET scanner). These gliders then collide into beehives, which are restored by a passing LWSS in Brice's elegant honeybit reaction. If the eater is present, the beehive would remain in its original state, thereby allowing the LWSS to pass unaffected; if the eater is absent, the beehive would be restored, consuming the LWSS in the process. Equivalently, the state of the eater is mapped onto the state of the LWSS.