Hi all,
I've discovered something rather neat. The Crayola "3d sidewalk chalk" you can get is actually something very cool. The glasses that come with this are actually ChromaDepth holographic lens 3d glasses. When you look at something through ChromaDepth lenses, the left eye sees the red component shifted rightwards and the blue component shifted leftwards, and the right eye sees the components shifted in the opposite direction.
What this means in practice is that red projections pop "out", towards the viewer, and blue projections pop "in", away from the viewer. Sadly you can't mix colours- yellow, for example, gets separated into its red and green components.
You can get these ChromaDepth glasses elsewhere for under a buck a pop, and I'm looking forward to taking a crack at designing something that'll make this look AWESOME. :-)