I first found lcamtuf’s site about machining–it led to my ill-fated buying/experimenting with milling machines. I have enjoyed reading all of his posts about electronics since then.
I’m not sure I 100% agree with the math-forward method of teaching things, but I obviously can’t argue with the simplicity with which he shows things working (I think the unstated element is that you need to understand the math first, which many don’t). Like Michal, I wish there were better intuitive ways to understand electronics without the hydrolic analogies.