I do spend a lot of time here on the BellaOnline forums. I don't see that as networking so much as sharing with other women about mey life, hopes and dreams...looking for personal advice, and some degree of an in-lieu social life. :-)
I have a few other forums, like one about RVing, one about blogging in general/specific, a coach forum I take part in (not free but very helpful), and, of course, Facebook and Twitter.
Twitter is now both fun for me and also a place to do article networking. Facebook is mostly for fun, although I do run a Fan Page for RunPee and add updates for people who want to know what is going on with new movie pee times and phone platform updates - RunPee Fan page on Facebook
You can make a fan page for people to get really targeted Facebook conversation. If you are a complete Twilight fanatic, you could, for example, fan
one their pages and get some other equally rabid conversation going.
Not saying that everyone need to spend more time lost on forums...but the right ones can really provide incredible free help, socializing or just plain entertainment in a free, interactive environment.
What forums do people visit a lot - like almost every day. And why do you bother going? Be honest!