This is basically for my own reference but anyone is welcome to use this or even rec me your own useful sites. In fact, I would very much appreciate you reccing me your own useful sites :)

WORLDBUILING (General)
On creating an Earth-like planet (heavy on astronomy)
Designing a fantasy world
World building links
Creating fantasy worlds
Creating a fantasy world by Sara Douglass
Patricia's C. Wrede's Wordbuilder Questions

WORLDBUILING (Specific)
Climate Cookbook
Fundamentals of physical geography
Calculating populations and demographics
World biomes
Major biomes of the world
Mythopet’s Manual (culture and religion)

LANGUAGE AND NAMES
Words maketh the culture
Everchanging book of names
What’s in your name?
Language construction kit

GENERATORS
Seventh Sanctum

LEGENDS, MYTHS, CREATURES AND PEOPLE
A guide to myths and legends in the British Isles

MISCELLANEOUS
Articles by Holly Lisle (haven't read anything yet but looks interesting)
Writing World
Pen & Sword
Weights and measures conversion