Dungeons & Dragons 3rd ed.-Magical Society World-Building Series

This torrent contains the books of the Magical Society series, put out by Expeditious Retreat press. They are a set of world-building aids, geared specifically for D&D 3E, but a lot of what they have to say is probably useful for anyone interested in fantasy world-building.

The books include:

A Magical Society: Beast Builder: A guide to creating monsters, including a consideration in how they would fit into the ecology of a magical world.
A Magical Society: Ecology and Culture: A guide to creating ecosystems and the societies of intelligent races, including how magic would impact the ecological and cultural world.
A Magical Medieval Society: Western Europe, revised and expanded edition: A guide to constructing fantasy societies inspired by those of medieval Western Europe, including the impact of magic on such societies. This edition includes a new chapter on medieval warfare and magic, plus two expanded chapters.
A Magical Society: Silk Road: A guide to overland trade in a medieval fantasy world.