Tools:

Editor Extensions/Game Toolkits/Visual Novels

Fungus https://www.assetstore.unity3d.com/en/#!/content/34184

Generate text, graphics
Tracery http://tracery.io/

Engines:
Game Maker – wiki available here
Python w/ Pygame
Unity game engine

Angel – created for EA game jams
Scirra
Love – 2D game engine
XNA with Visual Studio C#

UNreal

Environments:
Scratch http://scratch.mit.edu/
Greenfoot http://www.greenfoot.org/about/

Art:
Open Game Art

http://opengameart.org/

ALAN BECKER - Animating Walk Cycles
https://www.youtube.com/watch?v=2y6aVz0Acx0

Sprite Walk Cycle tutorial

https://gamedevelopment.tutsplus.com/tutorials/an-introduction-to-spritesheet-animation--gamedev-13099

GIMP

Sumo Paint

Inkscape

Lost Garden Graphics

Frogames [Dungeon Pack]

Google Sketchup

Wings 3D

Blender

Basic Maya modeling tutorials focusing on game environments:
worldofleveldesign.com

https://www.youtube.com/watch?v=MInKc7NafaI&list=PLOm0otrg7G6vPdbMrZs3O7ZXy0xQaFY5C

Other Maya tutorials:
3dtotal.com
free3dtutorials.com
3dm3.com
cgarena.com

Audio:
Audacity
SFXR: randomly generates sound effects

Hyperscore