Today I decided to experiment with the following equation:
2f + 3g + 1v when f = flash, g = gel and v = vaporizer
The result was a pretty cool blue fog surrounding my Star Wars DVD.
The flashes were snooted down to about a 2" opening with about 10" of tinfoil (I should probably buy some real ones someday), with the gels at the very ends of the snoots - not the common practice, but it worked in a pinch. The flashes were about 6-8" away from the fog and set at 1/2 and full power. One flash had two green gels, and the other had one blue gel. You can see which color was the strongest, even when the green-gelled flash had a higher power output.
I have never tried a shot like this, and it was kinda tricky to get my shutter speed and aperture to the point where both the fog and the DVD were visible. Hint: you need a pretty fast shutter and small aperture. It was pretty fun, so you might see more fog down the road.
Canon 5D Mark II
105mm - ISO 5000