Codemasters' rally racing game, Dirt 3, is totally free on PC through the Humble Store.
This Complete Edition normally costs $30 but you can get it for free from the Humble Store until 1 pm ET on Saturday.
But be careful, because the keys cannot be redeemed after 10 am PT on November 19.
You can grab the game here: Link
The Complete Edition includes the original game and all the seven DLC packs.