Free GM Resource: Adventure Generator from Dizzy Dragon Games
Fear not fellow Frugal GMs because the fine folks over at Dizzy Dragon Games have an absolutely free random dungeon generator that provides a lot more than a simple map!
You have three main options to generate your random dungeon: d20 Pathfinder, Moldvay Basic, and Moldvay/Cook B/X. You can set the appropriate party level or just say "screw it" and go completely gonzo (er...random).
I'm a huge fan of the fact that map is randomly generated and even has the rooms numbered, with additional information (assuming you want this) about the contents of some/most of the rooms. It is easy enough to populate a dungeon, tweak the rooms as you see fit, and be on your way in short order.
Spend less time prepping and more time killing! If that isn't your style, then just spend more time checking out the rest of Dizzy Dragon Games' freebies......