Isometric Game Art Pack - Extensive library of game art for indie devs
MagicaVoxel - A free lightweight GPU-based voxel art editor and interactive path tracing renderer.
Sketch This - Daily drawing challenges
Goxel - Goxel is a simple, but powerful voxel graphic editor with 24-bit color support, unlimited scene...
IsometricSass - Make isometric 2D objects without Javascript
Cubik Studio - Model in a unique cubic style. Start modelization with boxes. Move, rotate and scale cuboids.