Microsoft set up online forums after discontinuing support for their
sponsored newsgroup: start with Microsoft's Office Online help. FWIW, the
forums are monitored and moderated by Microsoft, thus giving them more
control -- but I've not heard complaints about them abusing their control.
The USENET newsgroup comp.databases.ms-access was begun in 1993 and
continues.
For specifics, a general search engine... Bing, Google, Ask.com, or
others... is a good starting point.
Larry Daugherty's suggestion of the Utter Access site is also a good one --
many knowledgeable Access users and professionals participate there, and
quite a few of the participants are Access MVPs. In fact, when Microsoft
looks for candidates for new Access MVPs, one major source is participants
at Utter Access (and, AFAIK, they've never picked one from UA who
dissapointed them).
The paucity of participation in the "zombie" (formerly Microsoft-sponsored)
newsgroups may partly due to the emphasis we observe on "web applications"
and on Microsoft's emphasis on Dot Net for application development.
Access has released some features for web apps, but none of them have caught
on in a big way. There are so many approaches, and tools for developing,
websites and web application that many do not see a big need to take up
another one... especially a "johnny-come-lately" to that niche market, and
more especially with the limitations that have plagued some Access features,
e.g., Data Access Pages, which came, never caught on, went, and haven't even
been supported since Access 2007.
There seems to be a reasonable amount of interest in Access as an
application front end, and SharePoint as a data repository in the last
couple of versions.