Here’s a few items I’ve enjoyed.
Excellent description on how to make things usable. Part of a good explanation is getting out of your own way — people shouldn’t think about what you are saying, they should be experiencing the concept.
Intuitive, geometric explanations of analysis, with some great diagrams for Euler’s theorem. It is fairly dense and I’m working through it, but I love the visual approach.
Illlustrated guide to Calculus & Fourier Analysis based on the question of how an “aaah” sound is recognizable despite a man, woman or child saying it. Great example of how to introduce a topic with real motivation.
I don’t use Word much these days, but PowerPoint is how I make my diagrams.
Excellent advice on improving your craft.