Historical/Fantasy Worldbuilding Resources:
[ACOUP Blog]
A Collection of Unmitigated Pedantry is a great blog in general, lots of stuff to read and resources
[PenultimateHarn]
Another blog full of useful resources and posts
[Behind The Name]
Name etymology
[Feudal Terminology]
Glossary of fuedal era terms
[Medieval Price List]
How much stuff cost back in ye olden day
[Medieval Prices and Wages]
More costs! I like to run very mercantile games
[Medieval English Wages and Prices]
You'll never guess, but its even MORE prices
[Firewood Calculator]
Might seem too granular, I wouldn't be a very fun GM for you if you think that
[Fantasy Worldbuilding Questions]
Questions to get the juices flowin
[Watabou's Procgen Arcana]
Procedural Map making tools, Watabou is great
[Eigengrau's Generator]
Fantasy town generator, mostly focused on demographics
[Medieval Demographics Tool]
A tool for generating medieval demographics
[Donjon Medieval Demographics Tool]
Honestly just check out everything here, Donjon has a ton of good tools
[Sometimes Reddit doesn't totally suck]
A reddit thread about the amount of land needed to support one person, good to keep in mind when designing your fantasy world