World Builders
A website supporting a world building distance education course. Reference material, lessons, downloads, and sample worlds.
http://curriculum.calstatela.edu/courses/builders/

World Building
An example of designing a planet, from basic physical assumptions to geography to weather systems and archeological remains.
http://www.suite101.com/welcome.cfm/world_building

Rich Staats' RPG / World Building Articles
Many interesting original and adapted articles of all aspects of gaming worlds, with much of interest to world builders.
http://www.geocities.com/dr_games/staats2.htm

Criar Mundos - Building Worlds
A step-by-step guide for creating original settings and incorporating realistic details. Various resources and references. In English and Portuguese.
http://criarmundos.do.sapo.pt/

Magical World Builder's Guide
Suggestions for creating consistent magic themes for fantasy settings, as well as general world building advice and resources.
http://www.web-writer.net/fantasy/

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.
http://www.fantasist.net/timeline.shtml

Worldbuilding
Indexed links reviewed for their relevance to gamemasters. With additional information on conlangs, fantasy names, and fictional religions.
http://www.bmarch.atfreeweb.com/Worldbuilding.htm