I began introducing "geography" with a globe, when my son was 3. Montessori always starts with the basics in any subject, and here it is simple: what is land, and what is water? I made "land and water trays" in pie pans with plaster. On our globe, we put a tack where we live, and one where Jesus lived. I made a relief map of Israel and a simple puzzle of the Holy Land. We have a model of the solar system.
Then I found a good but cheap ($9) wooden puzzle map of the 50 States at Target, and I glued a clear bead onto each piece for pegs. (This allows the child to easily remove one piece at a time.) Not expecting much, I was surprised to learn that my son had quickly learned the name, shape, location, and state motto (which was on the map) of nearly all the states. He had done this completely on his own, I had never looked at the puzzle with him before. I realized how effective puzzle maps could be, and put continent maps on my wish list - but because they are expensive, they sat on that list for quite some time! I would overhear him saying things like "look, I made Tennessee!" while eating a cracker, or "I'm going exploring in Montana!" while using his imagination at the park.
I got 8 containers for continent kits - one for each continent, and one for all of the continents (which is presented first.) Each kit has a book or two in it. I have coins from around the world, carved animals from Africa, chopsticks for Asia, and so on. (We will continue adding to these indefinitely.) I have 2 of the pdf. files from MontessoriForEveryone - the Continents and North America. These have 3-part-cards of animals, important places, and flags, as well as maps, which I made pin maps out of on cork board.

One challenge to puzzle maps is that they are large, and it took me a while to find reasonably-priced shelving to hold them. I paid $30 for some wire shelves from Target that are just right, 18" deep.
One reason I buy materials like this is that I'm confident they will resell fine some day when we are "finished" with them... And this is the type of material I'd be happy to share with another family for a few weeks or months at a time.