Isometric Game Art Pack - Extensive library of game art for indie devs
Unity - The multiplatform game creation tools for everyone.
Sketch This - Daily drawing challenges
Godot Engine - Feature-packed 2D and 3D open source game engine.
IsometricSass - Make isometric 2D objects without Javascript
Blender - Blender is the open source, cross platform suite of tools for 3D creation.