Valve details filmic effects used in Left 4 Dead
Speaking on the Left 4 Dead blog, Valve's gone into some detail about how general visual effects have been used to create Left 4 Dead's gritty atmosphere, including grain, vignetting, and whatnot.
It's interesting stuff. The zombie shooter's demo released yesterday for both PC and Xbox 360, so you can get a look at the end result first hand now.