Interesting question.

I've forgotten which page convinced me to start reading this site in earnest. It might have been "Generalization from Fictional Evidence", which is excellent, but that served a rather specific purpose for me and I'm not sure it'd do the same for others.

Looking over some of the sequences now, I think "Positive Bias: Look Into The Dark" might have the right balance of accessible and mind-blowing to hook a layman of no more than average mathematical sophistication. The 2-4-6 task is one of the more elegant ways of demonstrating both bias and possible countermeasures that I've encountered here.