Shock Absorber, a UK line of sports-bras, has a Flash-based boobies-physics simulator-NOT SUITABLE FOR WORK-. Plug in a cup-size and a level of activity, and it produces a 3D animation of breasts of that size bouncing free, bouncing in a regular bra, and hardly moving at all in one of their sports-bras. Extra geeky bonus points for including a 3D wireframe view, so you can see the pure physics of the jiggle.
It's like a lava lamp, but with boobies! God, do I love the inter-web.