An old Bullfrog game called Magic Carpet had a stereogram mode, as well as red-cyan 3D specs support.

http://en.wikipedia.org/wiki/Magic_Carpet_(video_game)#Innov...

In my browser (chrome) the image updates slowly and unevenly after each keypress, which interrupts the 3D illusion, and then I have to refocus on the new image. Otherwise, very cool.

Awesome game! Although I wish it moved one square at a time for each key press, making it less of a timing game.

And I really like their captcha for posting comments.