No recommendations from me, sorry. I don't participate anywhere but here. ... Oh, and in my journal. I write to myself a lot: it's good to have someone who understands me and will listen so patiently
. Seriously, I find it helps just to get stuff out; I don't actually need anyone else to hear it, I just have to get it off my chest.
Part of the reason why I don't participate elsewhere is a matter of time. Most of the writer's forums that I have seen seem to be mostly about reviewing each another's work rather than more general support/discussions (but not having participated on any, I may be selling them short). Anyway, the point is that if you join a group where people share their writing amongst themselves, it is only fair that you participate by reviewing the work of others (if you expect people to review yours), and such participation can be very time consuming. I can procrastinate well enough on my own without that sort of distraction.
(I'm not trying to say you shouldn't, just saying why I don't.)