I mentioned Physics Forums for math and physics, where you'd get all the feedback you could ever desire.

Communicating in meatspace with people I know personally is much more effective than over the Internet with strangers, all other things being equal (at least for me -- YMMV).

But otherwise you could find people elsewhere.

Like where? Not only would I have no idea where to find half a dozen physicists hanging out together in my home town, I'm not even sure there are that many physicists at all there.

It's just that the reasons to go certainly have nothing to do with the quality of instruction or something like that, which is what the OP was about.

What? Except possibly for the socializing thing, all the things I mentioned have to do with instruction.