Delta's D&D Hotspot posted about Gary Gygax and dungeon design.
Gygax on Dungeon Design
That kind of thing is why I've talked about the differences between writing for yourself vs. other people and the problems of other people's megagundeons.
I do much of the same - map it, put down a minimal bit of information that tells me the important stuff, make up a lot as I go (and note it down, so it stays in the dungeon), and just cross out the stuff that players have changed through their actions.
It's a really good way to go . . . but no way to write an adventure for someone else to run.