World Building - Contains mainly links to world design related articles and pointers to interesting sites.
World Builders - A website supporting a world building distance education course. Reference material, lessons, downloads, and sample worlds.
World Building - An example of designing a planet, from basic physical assumptions to geography to weather systems and archeological remains.
Guidelines For Creating Magic Systems - Compiled suggestions and discussions about the design of magic systems for roleplaying games and literature. Applicable to all genres.
Criar Mundos - Building Worlds - A step-by-step guide for creating original settings and incorporating realistic details. Various resources and references. In English and Portugese.
Fantasy World Building - Step-by-step tutorial for setting design, based on establishing a "world vision" for its cultural/geographic regions.
Magical World Builder's Guide - Suggestions for creating consistent magic themes for fantasy settings, as well as general world building advice and resources.
Timeline Generator - A web-based application that creates generic random events for a nation or region. The user can specify the starting year, number of years, and events per year.