Baltimore Science Fiction Society
Organization that promotes the discussion of and production of Science Fiction and Fantasy literature and hosts a convention known as Balticon.
http://www.bsfs.org

SF Canada
Home Page for SF Canada, Canada's national, bilingual organization of SF, Fantasy and Horror writers
http://www.sfcanada.ca/

Ardeon
A community of fantasy artists, writers and poets, featuring exercises and projects, reference library, member pages and discussion groups.
http://www.ardeon.org/

Sci Writers
Information about a free international writing club for fan fiction, science fiction, and fantasy.
http://www.angelfire.com/scifi/sciwriters/

World Science Fiction Society
Science fiction, fantasy and horror writing conventions.
http://worldcon.org/

Minnesota Science Fiction Society
Non-profit organization dedicated to furthering the appreciation of science fiction and fantasy literature. Social meetings, publications, fan conventions, electronic mailing list.
http://www.mnstf.org/

Writer's Resources
A collection a few essays and projects about writing science fiction.
http://www.cthreepo.com

NZSFW
For the promotion of science fiction and fantasy writing in New Zealand.
http://nzsfw.sf.org.nz/

Yahoo Groups: The Fledglings
A Toronto-area (Canadian) science fiction and fantasy writer's group.
http://groups.yahoo.com/group/the_fledglings/

Kansas City Science Fiction and Fantasy Society
Home of the Society, ConQuesT science fiction convention, and the Science Fiction and Fantasy Hall of Fame.
http://www.kcsciencefiction.org/