World-Design Tips: Things to think about when creating a game world.

Creating a Realistic Map: Use real-world geology and weather patterns to draw better maps.

City Design: Some useful (but very sparse) notes on city design.

City Features and Flavors: Tips on making realistic cities.

Medieval Maps: A collection of medieval maps of cities.

A bunch of floor plans for palaces, castles, abbeys, etc.

Creating a Religion: Tired of the contrived polytheistic religions found in role-playing games and written fantasy? Here's a long list of questions, to help you create a more realistic fantasy religion.

Mysticism and Shamanism: An article from Imazine Rolegaming Quarterly.

Making Fey More Alien

D&D: What is "Common"

Strolen's Citadel A large collection of locations, NPCs, items and other things you might want to include in your campaign.

Errant Dreams: This site has articles on character creation and world building.