http://www.bit-tech.net/gaming/2005/12/09/source_film_effects/1.html
Demonstrated here on Day of Defeat.
Now I don't know about you, but after HDR, I didn't expect the next 'big things' in engine capability - namely Depth of Field and Motion Blur - to enter the mainstream so soon. Valve have been beavering away in the background it seems, a logical solution to the 'broken promises' that frequently plague them.
Obviously this could all be construed as a bit much when you need the speed and untarnished vision to do well on the multiplayer battlefield, but for the casual gamer, for machinima, and for future single-player work (Aftermath, for instance, and hopefully for our mods too) this is manna from heaven.
I just hope performance-wise having at least a few of these activated will be viable.