rec.arts.sf.composition - join
The writing and publishing of speculative fiction.
High activity, 1036 subscribers, Usenet

rec.arts.sf.science - join
Real and speculative aspects of SF science.
Medium activity, 606 subscribers, Usenet

rec.arts.sf.fandom - join
Discussions of SF fan activities.
High activity, 526 subscribers, Usenet

alt.history.future - join
See also alt.yesterday.tomorrow.
Low activity, 200 subscribers, Usenet

rec.arts.books - join
Books of all genres, and the publishing industry.
Medium activity, 1024 subscribers, Usenet

alt.fan.grrm - join
Discussion on George R. R. Martin's "A Song of Ice and Fire"
Low activity, 297 subscribers, Usenet

rec.arts.mystery - join
Mystery and crime books, plays and films.
High activity, 806 subscribers, Usenet

alt.fan.heinlein - join
Fans of SF author Robert Heinlein grok this group.
Medium activity, 298 subscribers, Usenet

rec.arts.comics.dc.universe - join
DC Comics' shared universe and characters.
Medium activity, 1356 subscribers, Usenet

rec.arts.sf.reviews - join
Reviews of science fiction/fantasy/horror works. (Moderated)
Low activity, 120 subscribers, Usenet