Science Fiction and Fantasy Writers of America, Inc. was founded in
1965 by
Damon Knight. It is a non-profit association of
science fiction and
fantasy writers, mostly though not entirely in the United States. Membership is limited to professionally published authors; the minimum qualification is the sale of one novel or dramatic script, or three short stories. The SFWA boasts approximately 1,200 members as of
2001.
It awards the Nebula award each year for the best short story, novelette, novella, and novel.
See also http://www.sfwa.org/.