Where do questions along the lines of "how do I get my scanner (model number here) to work over the network with the latest OS X ?" (and similar questions) go?
(Obviously, they don't go on Stack Overflow.)
Is there a master list somewhere?
There is a master list.
And the correct site could well be Ask Different - as they say:
Ask Different is for Apple enthusiasts and power users. If you have a question about ...
and it is not about ...
... then you're in the right place to ask your question!
Super User is the most likely site - it is for general computing questions.
From the FAQ:
Super User is for computer enthusiasts and power users. If you have a question about …
- computer hardware
- computer software
- personal and home computer networking