September 30, 2010 – Team Fortress 2 releases the Mann-Conomy Update, a major patch that introduced the Mann Co. Store, Steam Wallet, and item trading.
Source:
TF2 Wiki
Valve unveils Dota 2 via Game Informer. The surge of web traffic crashed Game Informer’s website.
Source:
gameinformer
Portal 2 is released on multiple platforms and receives universal acclaim from reviewers averaging a score of 95 out of 100 according to metacritic.
Source:
Metacritic
Team Fortress 2 goes Free to Play (F2P) for all players alongside the “Über Update”.
Source:
Valve Press Release
Dota 2 is unveiled at Valve’s “The International” first event at Gamescom 2011. After this event beta test invitations were distributed.
Source:
IGN
Valve releases free Steam mobile application for all iOS and Android users.
Source:
Valve Press Release
Valve releases Source Filmmaker to all users after an open beta.
Source:
Source Filmmaker