Design Considerations: What do these boards give you?

Today's design thought to mull over: The Game Crafter's boards are super inexpensive to put in your game box. What can you do with a flat piece of cardboard (0r 4)? It can be a player mat, a player aid, a communal score sheet, an open market, an auction house, a map unto itself, a portion of a "map" (like in Reiner Knizia's Lord of the Rings), or a character sheet. What if you stacked the boards on top of each other? What if you rearrange how they appear in relation to each other? What about using single cards on a board to show various statuses or input-output relationships? Is there room for stacks of cards on or near your boards? How big a table can your game cover? What's the most fun you can put into a small physical space?