Here Is A discussion For You Suggestions For The Group (sensible please)
As MSTS, Trainz, and Railworks already have their own forums, perhaps you could track down some of the "free ones" you mention and start topics regariding them. A good one would be Rail3d (www.rail3d.net)
Rail3d is interesting -- I'll have to take some time to check that out. It seems more "train layout" oriented than MSTS, which is interesting to me since I do some modeling in O scale as well.