In Far Cry 3, you start out with a small portion of the map revealed (only the area you're in). That area fills the screen. In order to unlock new areas you have to activate radio towers in those areas. As you progress through the game and unlock more and more areas, you can continue to zoom out your map, giving a really great sense of accomplishment, and scope. I think this would work wonderfully in a game like Fallout 3. Hell, I wouldn't consider it a bad idea just to convert the radio towers idea. Would this be possible through modding?

I'm very tired as I type this, so please excuse any glaring grammatical or word mistakes.