Codemasters' racing game DiRT Rally is free for a limited time through the Humble Store. The game normally costs 34.99 euro but for the next 72 hours you can get it for free.
To get the game, just go to the DiRT Rally page on the Humble Store, and click "Get the Game". Once you get the game, it will be yours forever. The offer ends on Sunday, September 1 at 10 a.m. PT. But be careful, because the game cannot be redeemed after September 5.