If you still do old-school navigation with map and compass, the US Army’s Field Manual on Map Reading And Navigation is an excellent resource. You can buy a copy if you like, but there’s an HTML version here, Google Books has it available in poor quality scanned form here, and you can view/download a PDF copy from Scribd here (book is in the public domain). In one of the appendices, it has diagrams showing three different ways to fold a map so that you can view parts of it without completely unfolding it. The first two are self-explanatory:
The third one, the “Protection Method”, is a nifty way to fold a map so that it takes up 1/4 of its original size so that you can paste it into a notebook, but still have all sections of it accessible for viewing:
Had to try it out to figure out what was going on. After you’ve completed the full set of folds, adhere the undersides of sections A, F, L and Q to your notebook page. You can then view the various quadrants (A-D, E-H, J-M and N-Q) by flipping the sheets over the horizontal and vertical folds that cross the quadrants. Try it with a scrap piece of paper first :).
If you have a square map and want to try something different, you might try the Turkish Map Fold; I couldn’t quite figure it out myself.