Harry Potter

J.K. Rowling Official Site - The author's site
MuggleNet.com - The ultimate Harry Potter site
The Leaky Cauldron - More Harry Potter stuff
The Harry Potter Lexicon - Reference site to the world of Harry Potter

Star Wars

StarWars.com - The official site
TheForce.net - Site for the online community
Wookieepedia - Wiki site, serving as an encyclopedia for the entire Star Wars universe

Disney

MiceChat - A different look at Disney
DISboards.com - The DIS discussion forum
Pixar Planet - Celebrating all things Pixar

Star Trek

Memory Alpha - wiki site covering the entire galaxy