Various algorithms explained (eg. pathfinding, map generation)
http://www.redblobgames.com/

Links to tutorials about various topics (eg. pathfinding, AI, Game Design, OOP)
http://www-cs-students.stanford.edu/~amitp/gameprog.html

Videos from past Game Developers Conferences (GDCs)
http://gdcvault.com/free
https://www.youtube.com/channel/UC0JB7TSe49lg56u6qH8y_MQ

Great book (also online in html) on programming patterns (eg. Service Locator, Singleton, Event Queue)
http://gameprogrammingpatterns.com/

Game programming with SDL tutorial
http://lazyfoo.net/tutorials/SDL/index.php

Let’s make a voxel engine tutorial
https://sites.google.com/site/letsmakeavoxelengine/

Deconstructions of games (eg. what is the core loop of certain games, game design, features of games)
http://www.deconstructoroffun.com/