From the map screen, enter:

Cheat code:             Result:
unlockall               Unlocks all the maps for that difficulty.
relockall               Locks all the maps for that difficulty.

During the game, enter:
double                  Double all friendly armies.
half                    Havles all enemy armies.
empty                   Empty all enemy countries of armies.
booth                   Strengthen your enemies.
woohoo                  Ear candy.
explode                 Eye candy.
winmap                  Wins the currently playing game.
command-left            Go to the previous map
command-right           Go to the next map.