If anyone is looking for a more in-depth 'OpenGL For Dummies' tutorial, I wholeheartedly recommend Anton's OpenGL Tutorials^. It's written in a similar style to this blog post - plain English with simple minimal examples to follow along with - but it also goes into the math behind a lot of common rendering techniques.

It's really good, and I wish that I'd known about it years ago.

^ http://antongerdelan.net/opengl/