The best place for you to check would be the careers page of the various game publishers. At the very least you can get their contact information so you can call/email and find out where and how they recruit testers.
For example, the Monolith site ((http://www.lith.com/home.asp)
has a link right on the front page seeking testers.
Short list of game publishers below, you can probably find more:
Monolith Productions, Inc.
Creators of the LithTech Development System and games like F.E.A.R., No One Lives Forever, Shogo: Mobile Armor Division, and Tron 2.0.
Electronic Arts (EA) Develops interactive entertainment software for video game systems, personal computers, and the Internet.
Developer and publisher of interactive entertainment for a multitude of gaming platforms.
International producer, publisher, and distributor of video games for consoles and PCs. Formerly Infogrames.
Creators of computer games, including Unreal, Jazz Jackrabbit, and 7th Legion.
Developer, publisher, and distributor of interactive entertainment software for both core gamers and the mass market.
Official site. Includes game previews, downloads, tips, and more.
Develops, markets, and distributes video games for home consoles, personal computers, and coin-operated machines.
Develops and publishes for PC CD-ROM, Macintosh, and popular video games systems.
Publisher and developer of entertainment software.
Worldwide producer and publisher of arcade games, computer and video games, and gaming machines.
Game developer, publisher, and manufacturer.
Develops, publishes and distributes interactive entertainment software for the leading hardware platforms in the home video game market.
3D Realms Entertainment
Publisher of such games as Terminal Velocity, Duke Nukem 3D & Shadow Warrior.
Produces, publishes, and distributes interactive entertainment software.