This weekend Only, Valve is offering FREE online game play of its Team Fortress 2 for Windows on its Steam service. You will need to register for a Steam account in order to have access to the download. It’s FREE to signup for a Steam account.

If you want to continue playing the game past the weekend, you can purchase the full game at discount, $9.99 through December 20, 2009. FREE online game play of Team Fortress 2 from Valve ends December 20, 2009.