Even cross-platform play between PC and Xbox 360 is now free.
Microsoft has announced that its Games for Windows LIVE service - the Windows PC equivalent of Xbox LIVE - is now totally free. This means all the previously premium-only services such as matchmaking and cross platform play can now be enjoyed without a LIVE Gold account.
This applies to games new and old, and includes titles such as Gears of War, Shadowrun, Universe at War, Dawn of War II and Fallout 3.
Microsoft has also announced that a new Marketplace for Games for Windows LIVE will be rolled out this autumn. This will include new game content, demos, trailers and more.
You'll find more info over on the Games for Windows LIVE website.