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

• Culture-making checklist - neitherworldstories.blogspot.com
• Fantasy Worldbuilding Questions

Mythology

• Alpine folklore
• Aztec mythology
• Beowulf
• Finnish mythology
• Germanic mythology
• Greek mythology
• Kalevala
• Medieval legends
• Norse mythology
• The 4 stories we tell ourselves about death - Stephen Cave
• Worldbuilding: Fantasy Religion Design Guide

Astronomy

• Axial Precession
• Equinox
• Why is Winter Coming (Game of Thrones) - Deep Sky Videos

Demographics

• Biome reference
• Crash Course Biology: Ecology - Rules for Living on Earth
• Hypothetical types of biochemistry
• On the Ecology of the Orc
• Functional Model of the Late Medieval Village
• Medieval Demographics Made Easy - Tools: rpglibrary, donjon
• Medieval English society
• This is how I run guards in D&D - Tales Arcane

Culture & Politics

• Culture-making checklist - neitherworldstories.blogspot.com
• Government of a Late Medieval Village
• How much land does it take to support one human being?
• List of calendars
• Medieval Life & The Hundred Years War
• Medieval Life
• What it was like to visit a Medieval Tavern - Tasting History with Max Miller
• What happens when you visit a medieval inn? - Modern History TV

Economics

• Economics of English Agriculture in the Middle Ages
• Making Better D&D Towns: How to Make D&D General Stores - Master the Dungeon
• Medieval Guilds, Explained - The Generalist Papers

Climate & Ecology

Flags

• /r/vexillology
• 5 Basic Principles of Flag Design

War

Guides

• 25 Things You Should Know About Worldbuilding
• 7 Deadly Sins of Worldbuilding
• RPG World Building Series by sr2joker
• World Building Series by PhDnD

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

• Ancient Scripts
• Languages constructed by J. R. R. Tolkien
• Numbers in 5000 languages

Law

• List of Roman laws

Magic

• A Magical Medieval City Guide
• An Economic Analysis of Magic

Maps

• /r/imaginarymaps
• A pretty simple guide to basic tectonic scenarios, part 2.
• Ascension's Atlas Style Tutorial - Revised Presentation (video).
• Ascensions' Atlas style in Photoshop
• Cartographers' Guild* PlaTec - Plate Tectonics simulator
• Historical city locations based on defence and commerce
• History of cartography
• lands - World generator using simulation of plates, rain shadow, erosion, etc.
• Madness of a Modern Writer's Map Making Series
• Tectonics.js - 3D Plate Tectonics in Your Browser
• The Cartography Guild's "Cartographer's Choice" Winners
• The History of Cartography - 6-book series on cartography. PDFs available.
• Travelling on a horse: How does being on a horse compare to walking on foot? - Modern History TV
• King needs to travel: How fast and how far could he go on horseback? (we test it out) - Modern History TV

Guides

• RPG World Building Series by sr2joker
• World Building Series by PhDnD

Nobility and Politics

• Political institutions of ancient Rome
• Royal and noble ranks

Religion

• Alpine folklore
• Aztec mythology
• Beowulf
• Finnish mythology
• Germanic mythology
• Greek mythology
• Kalevala
• Medieval legends
• Norse mythology
• The 4 stories we tell ourselves about death - Stephen Cave
• Worldbuilding: Fantasy Religion Design Guide

Real Projects

• /r/collabworld
• /r/homemadeuniverse/

Software

• Donjon
• Flag Maker
• Free World Building Software
• Marvelous Designer - 3D tool for making clothing.
• Megacosm
• Planetary Habitability Laboratory - Software Tools
• TerraChronica
• Vue - Realistic scenery generator.
• World Machine - Terrain generator.

Random generators

• Donjon
• Megacosm
• Watawatabou

Unsorted

• http://io9.com/7-deadly-sins-of-worldbuilding-998817537
• http://terribleminds.com/ramble/2013/09/17/25-things-you-should-know-about-worldbuilding/
• If The Earth Had Rings Like Saturn
• The Relativistic Rocket - The math behind spaceships travelling near the speed of light. A calculator also exists
• 12 CASTLE misconceptions debunked by visiting REAL CASTLES! - Shadiversity

Space

• Atomic Rockets, projectrho.com: A must-read for any sci-fi worldbuilder.
• If The Earth Had Rings Like Saturn
• The Relativistic Rocket - The math behind spaceships travelling near the speed of light. A calculator also exists

TvTropes

Cliches can serve both as warnings and inspirations.

• Adventure-Friendly World
• Always Chaotic Evil
• Blue Blood
• Fantasy Counterpart Culture
• Fantasy World Map
• Five Races
• Forbidden Zone
• Heroic Fantasy
• Law of Cartographical Elegance
• Left-Justified Fantasy Map
• Literature: The Tough Guide to Fantasyland
• Low Fantasy
• Magic A Is Magic A
• Medieval European Fantasy
• Medieval Stasis
• Our Orcs Are Different
• Royal Blood
• Schizo Tech
• The Empire
• The Fair Folk
• The Federation
• Weapon of Choice
• World Building

War

• How do you realistically structure space battles and planetary sieges?
• Rocketpunk Manifesto's Space Warfare