Both of these interactive flash animations were on Boing Boing over the past few weeks, but I remember first seeing The Man Project something like 4 years ago.

Neverending Fall - a female body with limber limbs falling through an infinite sky of solid bubbles. Her body smacks/bends/slides over the bubbles. Sometimes she gets stuck and the only thing still moving is her chest, with each breath. You can fling her out of position and back into the fall with your mouse. I’d like to see this in full screen mode, projected on a wall.

The Man Project - bird’s eye view of a man’s body. His head follows your mouse with some lag, and the rest of his body slowly follows, in a liquid/slinky like effect.

Any others?