We looked at some of the 2010 finalists and winners in class, but from the site you can view finalists from previous years as well. Definitely worth a look.
For example, the image below is one of the finalist entries. By looking the dot in the colored image for about a minute, and then shifting your gaze to the dot in the white grid, you can create two different perceptions of after-images. For the full story, see the original entry.