SFcrowsnest.com: SCIFI-nder:Web directory of c. 2500 sites with a science fiction or fantasy theme.
About.com: Science Fiction Guide: Reviews, articles and interviews about SFF books, along with a links library.
AllScifi: Precision Search Engine: This search engine lets you search for science fiction novels by plots, characters, setting and action elements.
Best SF: A listing of links to online science fiction and fantasy short stories.
Classic SF: Database of fantasy and science fiction stories.
Del Rey - Author Sites: A list of links to online resources by or about authors who are published by Del Rey Books.
Locus Online: Links Portal: Directory of links to websites related to SF and fantasy, from science fiction trade magazine Locus.
Science Fiction Resources: Portal devoted to science fiction sites.
Scientists Who Write Science Fiction: A list of writers' better-known titles, and links to pages by or about them.
SF and Fantasy: A searchable database of science fiction and fantasy books.
SF: Made in Canada: Focus on Canada's science fiction, with pages on Canadian SF authors, magazines, actors and TV series.
The Science Fiction and Fantasy Book List: Attempts to list every SFF author and their works. Links to both official and fan sites.
The Ultimate Science Fiction Web Guide: Science Fiction information and a collection of biographies and links to other sites.