Recently the topicality of 3D questions has come under discussion. The main issue here is that Graphic Design's user base is unable to answer or handle a good deal of these 3D questions. I think the best solution moving forward would be to pass them off to different sites that are not part of the SE network, since the 3D.SE proposal on Area 51 was closed during the early days of beta. What are some good, friendly 3d forums to send these users to?
This is one of the largest 3D forums on the internet. I'm not sure how friendly it is, since I don't post there myself, however it is definitely well trafficked.
As mentioned above, cgtalk is the big one. Some additional ones include:
In my humble opinion, the best place to ask a 3D software related question is the software official forum, or the official un-oficcial :o).
I am not sure about the expensive packages like autodesk's, but that works on blender, sketchup, some render engines, etc.