Developer: Valve
Platform: PC
Genre: MOBA (Dota?) [same genre as League of Legends or Heroes of Newerth]
Join: The "Neogaf" guild in-game to play with other Gaffers, the mumble server to talk to some of Dota GAF.
Warning: If you are new to this game, be careful you WILL suck. This is not Team Fortress 2. The barrier to competence is long and frustrating. Theres a lot of information to absorb, a significant amount of it unintuitive. But we're here to help!
Updates: Large updates to the game typically occur once a month.
Where: Completely free, with no "gotchas!" like League of Legends or other F2P games. Download @ the steam store.