If you “Like” their Metro 2033/Last Light Facebook page, THQ will give you a copy of Metro 2033 for Steam for free. Clever PR for the sequel, Metro Last Light.
Here’s the link: http://www.freemetrogame.com/
That redirects here, for those of you who prefer direct links: http://www.facebook.com/MetroVideoGame?sk=app_395840630491782
In related news, the Humble THQ Bundle ends tomorrow. It now includes Titan Quest, the Path of War DLC for Red Faction: Armageddon and Warhammer 40k: Dawn of War for those who beat the average. The average is currently $5.70 and slowly trending upward.