iñigo quilez kindly provides his SIGGRAPH Asia 2014 Course Materials of ShaderToy with me via email. Thank you iq!

Thinking implicit: 2D, non polygonal shapes

• Coordinates and color gradients (That link is depracated, so I personally recommend this link instead)
• Shapping
• Texture Mapping
• Animation
• Reactivity
• More Media
• Yet More Media

Thinking implicit: 3D

• Raymarching
• Modeling (primitives and operators)
• Displacement
• Domain Repetition (and variation)
• Shape Blending

Thinking implicit: stateless animations

• Procedural Animation
• Blending Animation Curves
• Inverse Kinematics
• Simulating Physics
• Artificial Intelligence
• More

Pro-Tricks

• Anti-Aliasing (in distance fields)
• Depth of Field
• Analytic Motion Blur (not brute force 2D or 3D)
• Soft Shadows
• Computed Ambient Occlusion
• Painted Ambient Occlusion
• Analytic Ambient Occlusion (spheres and polygons)
• Atmospherics
• Shader-based Audio Generation