Ideally, I'd like a forum where rank amateurs like me can post
questions that may be answered by "respected regulars" with
lotsa knowledge on the subject.

I think you have to refine your overall goals/interests. There are
many places you can find out "how to use an op amp"
(or, "how an op amp works", etc.).

But, what you *want* to use that op amp for is probably where
you will get far more pertinent information/advice if you can
refine your needs better.

E.g., using an op amp to design a battery charger is different
than using an op amp to buffer the pickup from an electric
guitar or to implement a feedback loop in a robotic servo
controller.

A place that will give you "textbook" advice on how an op
amp works (or can be applied) will leave you wondering,
"OK, now how do I use that to ______?"

Not so! If you understand The Basic Rule in op-amp circuit design, you'll
see that there is no difference among these applications. Nor will you be
wondering how to do something.

National Semiconductor had an on-line seminar "explaining" op-amp circuit
design -- hostessed by a woman, of course -- and nowhere in it is The Basic
Rule even hinted at.

And Bob Pease had the nerve to tell me that my editing didn't improve the
quality of his (or others') writing!