As a fantasy and speculative fiction writer, I find worldbuilding fascinating. I have a whole series of posts on my blog about worldbuilding, and below is a list of them all, grouped in categories:
Setting & Geography
Creating a Fantasy World
Deciding on Your Fantasy Setting
What Planet Are You On?
Countries and Terrain
Inhabitants & Historical Context
Initial Character Ideas
Systems in Society
The Magic Behind Where Carpets Fly
Everyday Life & Culture
Career Choices in a Medieval Fantasy World
The Elements of Steampunk
The Elements of Dystopian Fiction
What is Young Adult Fantasy?