Enable 3D View in Left 4 Dead with $0 3D Glasses
 

what you’ll need:

Windows Vista or XP
Nvidia 8xxx series or later
Free superbowl 3d glasses
Left 4 Dead

First it enables the use of colored 3d glasses (AKA anaglyph)
Next, it changes from the default red/blue lenses to the superbowl colorcode yellow/blue lenses.
And finally, it enables the 3d Stereo drivers.

http://www.vgnerd.com/news/play-left-4-dead-in-3d/