mmmh I think we should use teamspeak, simply cause it makes speaking (and choosing who does) easier, although text sucks.. at worst, teamspeak+irc (i'll setup a new chan if need be) - msn and skype suck when there's more than 3-4 people...
I'd rather not go below nl100 though, both because there's already a lot of us and because we'd just be covering well-known basics (I'd like to speak about somewhat more "advanced" plays as much as possible - I would do NL200+, but I can't help as much at that level, plus there aren't a lot of us playing that level)
I could play for the first session, but (hopefully) I don't have many leaks, so there's less study material.. anyhoo, we'll see what's what in 2 weeks