AEG/Alderac Entertainment Group : (Shadis, Legend of the Five Rings)
Agents of Gaming : (Babylon 5 Wars)
Alternative Armies : (Flintloque, Firefight, The Duel)
Armorcast : Polyurethane resin models
Atlas Games : (Ars Magica, Once Upon a Time, Lunch Money, Pandemonium, more)
Avalon Hill : (Runequest, James Bond 007, Magic Realm)
The Castle Works Company : Model Castles
Chameleon Eclectic Entertainment : (Millennium's End, Psychosis, The Babylon Project RPG)
Chaosium (Chessex) : (Call of Cthulhu, Elric, Glorantha, Nephilim, Pendragon, Mythos)
Columbia Games : (HarnMaster)
Flying Buffalo Games : (Tunnels & Trolls, Catalyst, Lost worlds)
Five Rings Publishing Group, Inc. : (Legend of the Five Rings) Now at Wizards of the Coast
Guardians of Order : ("Big Eyes, Small Mouth", Toying with Destruction , Sailormoon RPG)
GHQ models
Grey Ghost Games : (Gatecrasher, Fudge "freeware", A Magical Medley)
Harlequin Miniatures
Hero Games : (Hero System, Champions, FUZION)
Holistic Design : (Fading Suns, Noble Armada, Carnage)
ICE (Iron Crown Enterprises) : (Rolemaster, Middle-Earth Role-Playing (MERP), Silent Death)
Imagine Role Playing, Inc. : (Imagine Fantasy System)
Imperium Games : (Traveller)
Inner City Games Designs : (Fuzzy Heroes, Wolfmoon & RPG accessories)
Judges Guild : RPG Magazines and accessories (Yep, they're back)
Kenzer and Company : (Knights of the Dinner Table , RPGs, CCGs)
Last Unicorn Games : (Dune RPG, Star Trek RPGs - TOS,TNG,DS9 etc)
Mayfair Games, Inc:
Pagan Publishing : (Call of Cthulhu supplements and sourcebooks , Delta Green)
Palladium : (RIFTS, etc)
Pro Fantasy : (Campaign Cartographer)
Rafm Miniatures : (Silent Death mins)
Scriptorium homepage  [Ragnarok Press] : (Ysgarth RPG, Fantasy Fonts, Oroborus etc)
Ral Partha 
Reaper Miniatures
R.Talsorian Games : (Bubblegum Crisis, Castle Falkenstein, Cyberpunk, CyberGen, Mekton, FUZION)
Rubicon Games : (Everway)
Steve Jackson Games : (GURPS, INWO, Car Wars, Ogre, Toon, Hacker, Dino Hunt)
Steve Jackson Games : Steve Jackson Games FTP server
Tantrix : (Tantrix strategy game)
Task Force Games : (Star Fleet Battles, Central Casting)
TSR : (Dungeons & Dragons, SAGA, Alternity) Now at Wizards of the Coast
West End Games : (Star Wars, Paranoia, Hercules, Xena)
White Wolf Game Studio : (Vampire, Werewolf, Mage, Wraith, Changeling etc)
Wizards of the Coast : (Magic : the Gathering etc.)

Meta-Industry Links

RPGnet : The Inside Scoop on Gaming
GAMA : The Game Manufacturers Association
CAR-PGa : Gaming Advocacy

Resources

TSR : Out of print products available for download, Now at Wizards of the Coast
The great net.book archive

rgfd faq : FAQ (Frequently Asked Questions) for the Rec.Games Dungeons and Dragons newsgroup

SCA : The Society for Creative Anachronism