A while ago, we bought Jack these place mats from Walmart . . . one with a U.S. map and another with a world map. During his afternoon snack, we've started playing a game with his goldfish (or whatever snack happens to be). I put a cracker on every state (or country) and he names the state and can eat a cracker.
He knows most of the states and quite a few of the countries. He asks to play the game regularly, and if we can't, he plays it himself.
Thank you, Pepperidge Farm.