A big list of worldbuilding resources available around the web.

Essentials

/r/worldbuilding - If you are into worldbuilding and you do not know about this place yet, this would be the first link you should click. They also have their own list of resources, many of which are also included on this page.

Starting a World

Astronomy

Climate & Ecology

Culture

Demographics

Economics

Flags

Guides

Inspiration

Crash Course World History: A series on the history of the world, covering pretty much everything. Notes.

Past Challenges from /r/worldbuilding: Random challenges for the world building community.

Language

Law

Magic

Maps

Nobility and Politics

Real Projects

Religion

Software

Space

TvTropes

Cliches can serve both as warnings and inspirations.

War