Melan's little article, Dungeon Mapping, is good stuff. Melan presents a careful analysis of a number of classic early Dungeons & Dragons adventure modules by means of diagramming the physical path available to the adventurers. This is a primer for anyone creating a megadungeon or adventurer module on how to take advantage of the physical boundaries imposed on players within a dungeon or similar structure.
Dungeon Mapping was critically important a few years ago as bloggers wrote about dungeon design and play. Melan's analysis continues to challenge me as a GM in my approach to dungeon design as well as my overall approach to gaming.