Valve's Steam downloadable game service just launched five free-to-play games, Spiral Knights, Forsaken Worlds, Champions Online: Free for All, Global Agenda: Free Agent, and Alliance of Valliant Arms. This marks the first time Valve has tried this strategy on Steam. Extra items and equipment will be available for a premium, but the games themselves are completely free. In order to entice more users, Valve is giving away free content that is normally premium for those that download the games this week.