Valve has begun accepting sign-ups for the Dota 2 beta. You can get yourself put on the "I'm interested. Give me one of those codes!" list over here.
That link is also where you'll find information about the impending gamescom tournament, including the schedule, how the teams are being matched up, and more. The timing is going to be crazy for those of us not in Europe, but I'm pumped to hear the broadcasters spout off phrases I don't understand, regardless.
There won't be a public beta of the latest Halo: The Master Chief Collection update
7:00 PM on 02.10.2015