Cross your eyes so that the two images converge to one in the middle. Your right eye will be looking at the left image, your left at the right, you will see 3 images and the middle one will be in 3D! This is the Mathematica spikey shape, and it was the answer to the flat-land problem I set a few days ago. [my code]
You should all check out Matthen. His content is insanely interesting and original.