Ledmeister's Doom Help and Information
 Doomworld  // Forums
 Newdoom  // Quickstart guide //  Wad Designer's Handbook
 Doomcenter
 Doom Help Service

Newsgroups:
rec.games.computer.doom.announce
rec.games.computer.doom.editing
rec.games.computer.doom.help
rec.games.computer.doom.misc
rec.games.computer.doom.playing

Gaming Companies:
idsoftware // idsoftware's ftp
Team TNT
Raven Software