Though I've had limited publication success (paid for 3 articles in 1999, nothing since), I recently had a friend, after having his story critiqued at www.critters.org, successfully win a Writer's of the Future contest. The site is approved by the Science Fiction Writer's Association (SFWA), and is worth checking out if you are serious about being a published science fiction writer.
If anyone has any experiences with critters.org, good or bad, I'd like to see their comments here with my post.
As always,
Qwain