Board Games
Mayfair Games: (http://www.mayfairgames.com/)
Steve Jackson Games: (http://www.sjgames.com/)
Wizards of the Coast: (http://www.wizards.com/)

Collectible & Card Games
Wizards of the Coast: (http://www.wizards.com/)

Comics
Dark Horse: (http://www.darkhorse.com/)
DC: (http://www.dccomics.com/)
Image: (http://www.imagecomics.com/)
Marvel: (http://www.marvel.com/)

Miniatures
Forge World: (http://www.forgeworld.co.uk/)
Games Workshop: (http://www.games-workshop.com/)
Privateer Press: (http://www.privateerpress.com/)
Reaper Miniatures: (http://www.reapermini.com/)

Role Playing
White Wolf: (http://www.white-wolf.com/)
Wizards of the Coast: (http://www.wizards.com/)