It’s been a while since I wrote anything, and since I’m at the FOSS4G2019 teaching and ranting about WebGL, it’s time to gather a few of my links. This is the list of links that I usually give away at the WebGL workshops I’ve been doing:
Extensive guide about programming shaders
Interactive The REPL & shader editor that I use in workshops
Another interacive shader editor, with some complex examples
Step-by-step tutorial on using stand-alone WebGL
Same as above, but for WebGL2
Full API documentation and some tutorials
Technology penetration statistics
Detailed iInformation about WebGL support in your browser /
Iván’s approach to tiled raster processing with WebGL /
Iván’s approach to displaying point data with a WebGL renderer

Some other libraries & frameworks:
Functional approach
High-level dataviz
Framework oriented to 3D scenes
Non-graphical math calculations

HTML-friendly OpenGL documentation (added here at 2020-11-12)
WebGL course (added here at 2020-12-03)

Reminder of how weird floating-point precision in WebGL is (source):

Name Total Sign Exponent Mantissa
WebGL1 lowp
WebGL2 lowp
Fixed precision
WebGL1 mediump
WebGL2 mediump
IEEE half
WebGL1 highp 241716
WebGL2 highp
IEEE single
Javascript Float32Array
IEEE double 6411152
Javascript Number
IEEE quad 128115112