It's the yearly Golden Joystick awards voting season, and this year voters will be able to receive either Civilization 5 or Mafia 2 steam keys.
You might have problems accessing the page due to heavy traffic, and sometimes voting may be disabled for a couple hours.
http://www.computerandvideogames.com/joystick/
Requirements: Making an account there (also validating), vote on all categories, submit, await up to 24 hours for the votes to be sent to greenmangaming which will email you the steam keys.
Already got Civ5 from it. Go quick, as this promo will last as long as they have keys on stock.
EDIT: Promotion has finished, voting results are live.
Edited by Friff, 25 October 2013 - 05:46 PM.