Some other good learning resources include

<atarget="_blank"href="http://learningwebgl.com">Learning WebGL</a>,

<atarget="_blank"href="http://www.webglacademy.com/">WebGL Academy</a>, and

<atarget="_blank"href="http://www.webglacademy.com/">WebGL Academy</a>,

<atarget="_blank"href="http://shadertoy.com">Shadertoy</a>, and

<atarget="_blank"href="http://glslsandbox.com/">GLSL Sandbox</a>.

If you're particularly interested in shaders, you might want to check out

<atarget="_blank"href="http://thebookofshaders.com">The Book of Shaders</a>,

<atarget="_blank"href="http://aerotwist.com/tutorials/an-introduction-to-shaders-part-1/">An Introduction to Shaders</a> or

<atarget="_blank"href="http://notes.underscorediscovery.com/shaders-a-primer/">Primer: Shaders</a>.