Giant Dungeon Ideas?

So.... on Friday we finished a D&D campaign and the votes were going around on who should DM the next one.

"HM*"
"HM"
"HM"
"HM"
*Was obviously my actual name instead of HM

._.

So I asked everyone what they were interested in for a campaign, and it was a 3/4 vote for an old-school dungeon crawl.

I've decided to go one step further and make it an campaign setting of an endless dungeon crawl, with little settlements in the corridors and rooms here and there. The only question is, how could I make this work?
I've decided to ask for ideas here, since I have less than a week to hammer this out.