Online game retailer Steam has started adding free-to-play games to its catalogue, with two shooters and three MMOs available right away. Champions Online lets players don superhero capes and masks in an alternative North America; Forsaken World mines European mythology; Spiral Knights offers co-operative, cartoon-stylized action. The futuristic, faction-based war of Global Agenda: Free Agent is joined by Alliance of Valiant Arms in the shooter category. What\'s in it for Steam? They\'ll be handling in-game transactions for players who want to purchase extra equipment, character abilities, or missions. For players, there\'s the convenience of using one intermediary when it comes to making those purchases, plus the additional prospect of accumulating Steam Achievements in Champions and Spiral Knights. The news comes soon after GamersGate announced its own FreeGames project, in which participants can play full retail games that show advertisements on start-up.