Wookieepedia: a Star Wars Wiki. Probably the most detailed and up-to-date Star Wars resource on the web today.
Star Wars Atlas: a comprehensive galactic map.
StarWars.com Databank: an official source for info, including images.
The Unofficial Star Wars Encyclopedia: a huge resource for looking up Star Wars terms.
Stargate SG-1 Lexicon: encyclopedia for lots of terms.
Stargate Tech Centre: fantastic site for Stargate technology.
Encyclopedia Mythica: details on real mythology.