How about another illusion just published this year, 2007: van der Helm's “sticking cogwheels.” You can read about it, and see a wonderful Flash animation, on Prof. Michael Bach's website, just by clicking on the image above. When the inner (red) wheel rotates within the cutout in the larger blue wheel, you will see that the red wheel continually appears to “stick” and “unstick” as it turns. Prof. Bach's page has a link to the discoverer's web page, which shows a variety of variations of the basic illusion. On Prof. Bach's page you can use the sliders and buttons to vary several aspects of the presentation; note that it is fairly easy to find situations in which the sticking illusion vanishes. [If you are using an older web browser, this page may not display properly and may even crash your browser.]