At the moment I have a protoype working for a top-view dungeon crawler.  It's inspired by those old  rogue-like style games where graphics were not important. 

It is a single screen game, so its far simpler to code and manage than hecklifter (and also means I might complete it).

The algorithm is:
- set the entire screen to fog, except the outer border.
- create a grid (I think I made it 6x5) and then randomly connect them with openings.  This means the rooms are small (about 3x3 plus walls).
- You start in a room with the stairs and un-fog the room and its openings. 
- As you enter another room, the fog lifts so you can see what it has in it, including additional openings. 
-When you encounter stairs, it automatically generates a new level.

Does anyone know if there any game similar to this on the NES already?