I have tried several sites but I currently don't use any of them. Sometimes personal and family issues tend to eat up my time, so when I'm in a period like that I try to hunker down and save what time I have for my writing.
I don't have the time or desire for chatrooms, and I only frequent newsgroups (like rec.backcountry) to rile up the self-appointed outdoor "experts" - who in their turn, then post false "reviews" about my books on amazon.com. Such phony reviews are not to be taken seriously, and it's pretty clear that the people who post them haven't actually read the books the claim to hate so vehemently, but it gives me a chuckle.
Beyond that, some of the magazines I write for - Michigan Country Lines, Backwoods Home, Modern Survival, et al - post some of the articles they've bought from me on-line.
I'm a member of Broad Universe (http://broaduniverse.org/) and EPIC (http://www.epicauthors.com/) and frequent those mailing lists.
I love Michigan writers, and recommend that people start writing groups in their area to build the creative process of writing. We did that in Glen Arbor at The Cottage Bookstore and it was wonderful.
I use Querytracker.net, which is a nice tool. I don't know that I would have actually sent any queries without it.
I like Open Salon; I've toyed with FieldReport and Facebook ... but I don't need that many friends!
I go onto Writers.net because they have forums for everything. Publishers, editing, agents, etc. Everyone on the forums can relate to your experiences or help you with problems which is great!
Lately, I've been going onto teenagewriters.com because, being teenagers, they can relate to what I'm writing (as I write for YA) and they can give you better feedback on excerpts if it is a situation that teenagers would get more than adults.
I am the founder and adminstrator of two online networks:
I also use various other sites on the internet to share experiences and information such as Myspace and my own personal blog page at www.deborahsimpson.org.
Poets & Writers.
I don't frequent any specific sites.
Whomever approaches me.
None. I get online to research, browse around writing sites, but do not share writing experiences or information....other than contributing articles in competition on the writing site, Helium.
Writing doesn't allow for much leisure web browsing.