Fighting games. I wasn't too surprised not to find communities for specific fighting games (other than Guilty Gear which I don't like) but no general community either?
A non-pornographic femboy and/or femboy discussion community (a pornographic one exists.) I'm still deciding whether I want to go back to Reddit or not and the thing that almost prompted me to go back right then and there was wanting to ask a question about fitting into women's clothes. This I think might be too niche to be useful on anything other than a big site.