Hey there,
My suggestions would be Facebook, Tumblr, and ->-bleeped-<-.
The FB group I would specifically suggest is FTM Moderated. I'm not sure if the admin still hangs out here, but he keeps it monitored. In addition, it's a Secret group. So not only does it not show up anywhere on your page, it isn't even searchable. Invite only. So unless your friends are transgender men, they have no way of gaining access to it.
Tumblr doesn't really lend itself to group convos, but there's a pretty healthy trans community there. Track the FTM tag, follow some guys, talk to them. Everyone I've ever spoken to has been friendly.
On ->-bleeped-<-, the FTM sub->-bleeped-<- is very good. Lots of good discussion, info, links, and post-op folks who are willing to talk about their experiences.
But yeah. That's what I've got. If you'd like an invite to the FB group, send me a PM and I'll get you in.