You've probably seen Pi visualized with color [Flickr]. Now, you can play around with it here (change color of digits) : http://www.endofart.net/pi/ [Java applet] - Thanks Martin!
Yeah, I thought it was a stereogram too. Took me a bit to realize it was just a visual representation of pi by assigning each pixel a color corresponding to the appropriate digit (as opposed to a stereogram picture of pi itself).
--TwoDragons