Asking open-mindedly and genuinely: what, for you, comes to mind as an especially useful and/or powerful idea uniquely articulated by foucault?
Biopower is the most famous one, but I actually think his greatest contribution was to make philosophers pay more attention to the ways in which epistemic systems and ways of organizing knowledge are connected to political power.
I actually think his phd thesis "the history of madness" is his best work. It encapsulates much of the subject matter that would occupy him (knowledge and power) in a domain that's easier to understand than some of his later arguments, and it predates his adoption of a more contorted literary style (or maybe the translation is just better, idk).
Ian Hacking also has a great text that extends Foucault's work "Historical Ontology" that picks up many of the chief ideas in a far more lucid manner for those of us who aren't fans of the later continental style (which if I'm being honest, was always a little too concerned with being obtuse just to sound intelligent)
Just to volunteer an example: An editorial by Assange that explicitly called out the panopticon was on my mind today.
The rise of "meta glasses" and reading ICE also wishes to employ them was what reminded me of this I believe.
Sociology (like philosophy, like math) is one of these subjects were a good teacher makes all the difference. I guess true of any subject. Many people come away from a subject thinking it's bunk or not relevant to them for all sorts of reasons. Teachers are not meant to be babysitters or proctors they are supposed to offer context and connect the dots.
The amount of bad teachers (it is a hard job) is quite staggering. Education is in large part a mess because we've tried to scale a system that was designed for the very few to the very many without the proper investment.