Online game distributor Steam has begun offering free games for its users in a newly launched "Free to Play" section.

The games are completely free to download and play - although like free Facebook games, there are small charges associated with micro-transactions within the titles. You don't need to register a credit card, or have a Steam Wallet - although there may be some limitations within the games if you don't (to prevent spammers).

The first five free titles on offer are four MMORPGs; Global Agenda: Free Agent, Champions Online: Free for All, Spiral Knights and Forsaken World, and the FPS Alliance of Valiant Arms. Only one of the titles, Spiral Knights, works with Mac OS X though, you'll need Windows for the other four.

Each day there will be a game of the day in the "Free to Play" section, where exclusive in-game content will be available.

"The introduction of Free to Play games is another example of the constant evolution of Steam," said Jason Holtman, director of business development at Valve.

"Free to Play games offer new game genres and game experiences for customers, while offering developers and publishers new revenue opportunities and the ability to reach customers in areas of the world where the traditional packaged goods model is less popular than F2P."