I just had an interesting idea for how to manage the map & key for an evolving dungeon. The assumption is that each time a bunch of adventurers go in there and cause trouble, a substantial number of facts about the dungeon (e.g. what monsters live where, what treasures exist, and so on) will be altered. Traditionally I've had two separate things: 1. the dungeon map with numbered rooms, 2. the dungeon key, describing what's in each of the numbered rooms.
I've found that two problems arise with this system of separate map and key. Firstly, the simple issue of having to flick back and forth between various sheets of notes, and of having to correlate the map to the descriptions. Not a huge deal, but there might be an easier way. Secondly, the problem of what to do when things change in the dungeon -- treasures are looted, monsters killed, etc.
So the idea I had, which should help with both these issues, is the following: make a dungeon map as usual, but without numbering the rooms. Then scan the map and divide it into four quarters. Zoom each of these quarters up so that it fills a whole page, print these. So you'll end up with one large scale map (at a normal scale of 10' per quarter inch, or whatever), which is the one you can stick to the back of your DM's screen for an overview of the level as a whole, and four zoomed in quarter maps.
The descriptions of what's in the dungeon should be written straight onto the maps of the dungeon quarters, in pencil so it can be modified as the place is demolished by zealous adventurers.
I reckon this'd be a really nice way to work with dungeons, would enable quick & easy restocking / modifications to the dungeon in response to PC actions, and would encourage an anti-perfectionist attitude where the dungeon is a living play-aid, rather than a publishable document. I'm definitely gonna try this out for my next dungeon!
(Another way, of course, might be to just map in the first place at a greatly zoomed-in scale. I guess I'll try both methods and see which works out best for me.)