Science Fiction Resources:
(Please note that this is not a complete list.  These are merely the ones I use regularly.)

Books:

•   Science Fiction: The Illustrated Encyclopedia.
  By John Clute.  Arthur C. Clarke himself called this book "One of the best and most comprehensive books ever done on the subject..."  Covers, in brief, the history of Science Fiction from its birth to modern day, complete with illustrations and interviews.

• The Encyclopedia of Fantasy. 
  By John Clute and John Grant.  Like its companion volume, The Encyclopedia of Science Fiction, this massive reference of 4,000 entries covers all aspects of fantasy, from literature to art.

• The Encyclopedia of Science Fiction.
  By John Clute and Peter Nicholls.  This is THE Science Fiction reference book.  Sci-Fi author Samuel R. Delany calls it "..the most intelligent, wide-ranging, and richest reference work on science fiction ever assembled. To date it is the indispensable volume on the topic."

• The Sci-Fi Channel Encyclopedia of TV Science Fiction.
  By Roger Fulton and John Betancourt.  From "My Favorite Martian" to "3rd Rock from the Sun", this guide features virtually every sci-fi series in the past five decades, making this the definitive volume on televised science fiction entertainment. Includes 2 photo inserts, and even has a synopsis of the short-lived and rarely remembered Voyagers!
  

• The Legacy of Heorot.
  By Larry Niven, Jerry Pournelle and Steven Barnes.  An interesting retelling of Beowulf, the classic tale of man vs. monster.  However, the story is set on a world far from Earth which is the site of the first human attempt to colonize another world.  The trio of authors build a compelling cast of characters and set them in a vibrant environment with a rich ecology.  If you enjoyed Beowulf, read this book.
  

• Beowulf's Children.
  By Larry Niven, Jerry Pournelle and Steven Barnes.  A less-than spectacular sequel to their best-selling novel The Legacy of Heorot (see above).  However, if you liked the characters in the first book, you'll probably like this one too, and it does have some wonderful concepts floating around in it.

Movies:

• Star Wars Trilogy Special Edition. 
  The ultimate Science Fiction epic.  This boxed set (now hard to find since LucasFilm Ltd. removed it from the market) is the complete revised Star Wars Trilogy, comprising the Special Editions of Star Wars: A New Hope, Star Wars: The Empire Strikes Back and Star Wars: Return of the Jedi.  A must-have for any serious Science Fiction fan.

Web Pages:

• Star Wars Official Website.  If you're a Star Wars fan, this is the only place you need to know about.  Run by LucasArts, it has up-to-date information about EVERY aspect of Star Wars, including information on the original trilogy, the upcoming movies, books, comics and collectables.  It also includes a very interesting article on the mythological sources that Lucas drew from while crafting his epic.

• The Mining Co. Guide to Fantasy/Sci-Fi Books.  An extensive collection of links and articles concerning fantasy and science fiction books.  Includes an excellent search engine, reviews, critical commentary, and links to related sites.  An excellent starting point for almost any science fiction search.

• - The Science Fiction Resource Guide contains an extensive collection of links to SF resources on the Net. Subject areas include other archives and resource guides, authors, art and artists, bibliographies, movies, television, bookstores, book reviews, role-playing games, zines, etc. Some of the topics include Anne Rice, Bram Stoker, Jules Verne, H G Wells, Star Wars, Star Trek, nanotechnology, vampire fiction, and more. The site is maintained by Chaz Boston Baden.  (Thanks to them also for providing this wonderful description!  Very convenient!)

• The Star Trek Continuum - THE source for information about Star Trek.