The Grognardia article on Dungeonaday stirred up some pretty interesting comments about an RPG blogger mega-dungeon project (thanks to The Society of Torch, Pole and Rope for pointing those comments out). "What a great idea" I thought, "but what a monster to organize."
After sleeping on it (or rather not sleeping on it, since I kept waking up with thoughts of mega-dungeons floating in my head), here are a few random thoughts on how such a thing might be coordinated.
(Edit: Looks like Grognardia took the bull by the horns here)
I'd define a level as the unit of contribution, using something like Chgowiz's one page dunegon template as the map space each level uses. I'd also define the vertical thickness each level takes up so there's some sort of geometric sense to the whole thing. Once I had a level defined I'd define a layer as a grid of M x N levels and apply labels to each axis, then I'd stack up a whole bunch of layers to form the structure of the entire mega-dungeon. The whole mass ends up being a giant cube of one page dungeon levels. Pick axis labels that match well with a spreadsheet program and it becomes pretty easy to track level ownership using a multi-sheet spreadsheet. Even a fairly small layer size creates a huge level count, ten 10x10 layers is 1000 levels!.
The top layers need some special attention since they provide the entrances from the outside world (assuming a standard sort of top-down dungeon crawl). It's probably worth defining some levels here as empty, representing areas on or above the surface. Others might be allocated as 'open air' dungeons, ruins, tombs and the like that are above ground.
Once there's a structure to hang levels on builders can start planning. Since there are many people involved, I'd implement some minimum requirements for each level being built. Builders would need to know the connectivity (in all directions), theme, construction (caves, dwarven mines, etc.) and primary inhabitants of neighboring levels. I'd set some minimum connection count to insure adventurers can traverse the whole mass. I'd also think some sort of bleed-over wandering monster list would be a good thing.
Of course there are many other elements that have to go into this, creativity and teamwork being two big ones. It may be worth laying out some very broad themes for portions of the mega-dungeon (the north half of layer three is primarily catacombs). Individuals might want to stake claim to connected groups of levels to implement grander plans than those allowed by the base level plan. A central bestiary and treasure list might be a good idea for ease of reference.
In closing, man what a great idea! I'd love to help.