Didn't get an invite to the DOTA 2 beta, but you want to see the game in action? Today is your lucky day, with Valve launching a free spectator app allowing users to view recent or live matches, plus every match played during the upcoming International tournament.
You can watch the matches unfold from the perspective of players or via a directed view of the match, complete with commentary. Eventually the spectator client will be rolled into the final game client when DOTA 2 officially launches, but when that happens we still don't know.
By Stephen Heller