Are you an aspiring sci-fi author? Looking for a community of fellow authors to share insights and provide constructive criticism? If so, you might want to consider the Online Writing Workshop for Science Fiction, Fantasy and Horror.
I love the fact that they're using technology to create a virtual resource center for all types of authors, from the complete novice to the seasoned veteran. They've even created a wiki that "offers workshop members a way to interact that's richer and more useful than just a discussion mailing list."
Although the service isn't free, the $49/year membership fee is a bargain when you consider all the features this site has to offer.