Humble and Codemasters are planning to give out DiRT Rally for free. The offer is limited, however, and it will last until September 1. As soon as the week is over, the game is likely to be delisted (as it always happens with similar offers). Of course, Grid 2 was available for a while even after the free period was over, but the same cannot be said for DiRT 3 and Showdown.

So yeah, use this opportunity and get the game while it lasts if you want to save some bucks for other games. Just go to the official website and add the game to your Steam account. And yeah...enjoy of course!