Not sure whether we will have a forum in the long run, but as some people requested it, we put something online.
http://www.projectmagenta.com/forums
This will be there for the next month on a trial basis.
We used to have a very active newsgroup, and I am a bit partial to mail reader based solutions, but perhaps this will prove useful as well. So feel free to enter content.
I also never get tired of encouraging anyone who wants to post photos or information about their own simulator… you can do that in the Sim Builders Blog (link on the right hand menu).