From my experience Featherweights is pretty much dead. I tend to stick with the 20-somethings (though I'm 19) at least until I get home (on summer vacation still) and can better commit to a strict diet plan - then I'll probably pop over to South Beach, too. Lots more activity in all of those. You don't just have to stick with one group, either! Take part in any group you relate to.
A lot of members find that using email or myspace also helps them get support when they're not on the forum. It's an idea, too.
Good luck with your weight loss