Holy shit bro game sales every where on steam!
Some examples :
Every Call of Duty game besides MW2 for $30
Unreal tourny pack $13
Bioshock 2 $15
Killing floor $5
Trine $4
Some deals like Bioshock 2 are just for today and I'm assuming their changing up the deals everyday but most are for 10 days
http://store.steampowered.com/
^^for all game sales^^