I have these in, what seems to me, a logical order. However, in practice I do jump around between them to plan ahead, solve problems, organize my thoughts and do whatever it is I need to do to come up with a fun playable dungeon design.
- The One Page Dungeon: Here is a modular approach, popularized by Stonehell Dungeon (which utilizes a Two Page Dungeon) and a string of One Page Dungeon contests. Basically, the dungeon is mapped out in 300' X 300' modules (or similar size) with the map and the map key fitting onto one page (or two pages). Here are some early posts from Sham's Grog `n Blog (here and here), ChicagoWiz's RPG Blog (here), and The Society of Torch, Pole and Rope (here) that provide more detail and insight.
- The Architect DM Series: This series of blog posts on Critical Hits are not profound, but they do serve as a good reminder that a dungeon is a physical space underground (two sample posts here and here). I try to include basic engineering elements, such as columns. More importantly, it is a good reminder to have lots of "black space" or solid rock to physically support the rooms and passages. Part of this is my own personal dislike of dungeons that have no apparent means of support the roof (you know, those dungeons where every space on the map has been used (like Gary's map pictured here). My undergrad degree is in geophysics, so I feel a suprising need to have structural integrity in my dungeon (but at the same time, I don't worry about what dungeon critters eat...go figure).
- Map Flow/Decision Tree Approach: I wasn't sure what to call this approach to dungeon design. "Melan," in a now-classic thread post, analyzed a number of TSR/WotC adventure modules, by looking at the pathway(s) available to player characters as they physically moved through the module (you can find Melan's text here). While he restricted his analysis to modules (with smaller dungeons), his thoughts and observations have helped me think through how player characters move through space. I have found it particularly helpful in giving players opportunities for decision-making based upon the physical layout of the dungeon.
- Node-Based Dungeon: Another way to diagram and plan dungeon areas, factions, and encounters. Keith Davies has several posts on his blog, In My Campaign (you can read some of his node-based dungeon posts here, here, and here). Dungeon of Signs also has this post. [Update 3/8/13: Keith added links/landing page for his Node-Based Dungeon posts; you can find it here]
- The Dungeon, the Underdark, and Beyond: I am a big fan of the Underdark concept. I love the idea of underground cities, complexes, and sites connected by stairs, rivers, passages, and portals (like this and even this).
*Thanks to the Happy Whisk for providing me with this useful unit of measure.