AntiCheat Inc - Battlefield 2142 and America's Army system administrator anti-cheat community.
Cheat Police - Register for free to get anti-cheat software and bust them cheaters!
Counter Hack - Wiki offering resources to combat cheating in multiple games.
DMW - Third-party anti-cheat software originally developed for "Medal of Honor: Allied Assault" and expanded to protect other games.
GameGuard - Anti-cheat software from INCA Internet.
PBBans - Offers a "Master Ban Index" among networked game servers.
PlayNoEvil - Weblog focusing on game security and on the farming and sale of game valuables in online RPGs. Partial focus on Asia.
PunkBuster - Anti-cheat software incorporated in some of the more popular online, multiplayer shooters, including the Battlefield series.
PunksBusted - Anti-cheat organization, supporting all PunkBuster enabled games. Home of the Auto-MBL, a large scale ban list system with thousands of member servers. Forums available in English, German, and French.
Respected Admins - System administrator community dedicated to anti-cheating with a focus on Punkbuster supported games.
SecurePlay - Offers programming libraries to incorporate anti-cheat measures which work even if the source code is compromised.
Wikipedia: GameGuard - Encyclopedia article covering the software, including criticisms.
Wikipedia: Valve Anti-Cheat - Encyclopedia article covering anti-cheat measures used in Counter-Strike, Half-Life Multiplayer, and other games distributed on Valve's Steam platform.