Although there are still some independent, newsreader-based discussion groups out there, the majority of the AutoCAD action nowadays happens on Autodesk's own moderated discussion groups. These are user-to-user groups, but even so, you frequently see Autodesk employees jumping in to answer questions in their areas of expertise — sometimes on their own time!
To see what's there, point your browser to www.autodesk.com/discussion. There are product-based discussion groups for AutoCAD and AutoCAD LT.