Upgrading the 'Vanishing Fog' from the old illusions page, we have produced these nifty variations. I went through several different designs (about 40) to see which worked best, and the below three made the shortlist. I reckon it would be hard to top 'em.
This one below is the featured version. As before, stare at the red dot in the middle of the top picture (keeping your head perfectly still), and then after a minute or two, scroll down to the less-contrasty version just below it. Then stare into the middle of that one, and you'll find that a spangling star will start to 'twinkle'.
This one is similar to the above, and cooler in one way. Give your eyes a short break, and then stare into the middle of the left pic, and after a minute, look at the right pic, and either stare into the middle as before, or follow the little circle round to truly witness what looks like a strange light source rotating around the scene!
Waves of Confusion
A different effect again. This time, there's a wavy look, and the curves will switch in an odd way between vertical and horizontal!