Steam, owned by Valve, is no stranger to free games and has both given away games, such as Alien Swarm, as well as hosting free weekends, where fans of a title, most recently Call of Duty: Black Ops Multiplayer, can enjoy a game for one weekend absolutely free.
What Steam has never attempted, until now, is support of Free to Play (F2P) games. As of June 14 Steam has begun to include F2P games in the Steam Store. The first wave of titles are Spiral Knights, Forsaken Worlds, Champions Online: Free For All, Global Agenda: Free Agent and Alliance of Valliant Arms.
To kick off the first week of F2P games on Steam, the company announced that starting on Wednesday, each day will have a different feature F2P game, and by purchasing the game on that day, players will receive exclusive content. The bonus week will draw to a close on Sunday and more information has been promised in the coming days.
For the full press release, you may go here.