Game Web Sites and Officials Blogs:

Chronicles of Darkness

Pathfinder and Starfinder

Dungeons and Dragons Home Page

D&D 5th Edition Unearthed Arcana

13th Age

 

Game SRD’s:

Fate Core SRD

FATE Core Toolkit SRD

D20 Pathfinder SRD

Spirit of the Century SRD

Dungeons and Dragons 5th Edition SRD (there are others you can google, too)

13th Age

 

Game Running Resources:

Roll20 (Don’t run an online campaign without it!) 

Kobold Fight Club Encounter Builder

Hero Labs tools for character and state tracking

 

Homebrew Sites and Inspiration:

D&D 3.5 Homebrew Wiki

Homebrewery for beautifully formatted Dungeons and Dragons 5th edition homebrew material

DM’s Guild