Halloween III: Season of the Witch (1982)
Halloween 4: The Return Of Michael Myers(1988)
Halloween 5: The Revenge of Michael Myers (1989)
Halloween: The Curse of Michael Myers (1995)
Halloween H20: Twenty Years Later (1998)
Halloween: The Homecomming (2002)
Timeline of the Halloween Saga
Halloween: The Curse of Michael Myers, the Producers' cut
Here is Kevin Willamson's origional 7 page treatment for Halloween H20
Offical Halloween Site
Loads and loads of stuff.
73 Miles to Haddonfield
Lots of good stuff.
Halloween
Some cool stuff.
Orange Grove Video
A small video store that will sell you some quality VHS tapes of the alternate versions of Halloween II, Halloween 6, and even the film-makers' commentary from the Criterion Laserdisc version of Halloween. The quality is about what you would get taping from TV in EP mode on your home VCR, which is about the best bootleg you're ever going to find.