http://www.sff.net/
SFF Net is an online community for "Genre Fiction", although as the name suggests, it is dominated by science fiction and fantasy. SFF Net offers email, newsgroups, IRC, and webhosting. Newsgroups and IRC are open to the public (news.sff.net and irc.sff.net); other services come with paid memberships.
The primary distinctions of SFF Net are the large number of authors, editors and artists who call it home, and the extensive discussions in sff.net newsgroups. Many major sf authors host their web pages here and participate in discussions about their work.
See http://www.sff.net/sff/news/ for a list of newsgroups and http://www.sff.net/people/ for a list of webpages.