Depth perception relies on stereoscopic vision, with each eye receiving an image from a shifted perspective. The shift is interpreted as depth information by the brain. With this method, the image that is meant for each eye is tinted red or blue (cyan, actually), and the viewer wears a pair of special glasses with one lense tinted red and the other cyan, so that each eye only sees the oppositely-tinted image, and the image appears to be 3-dimensional.

• images to print
• red-cyan glasses (paper ones are inexpensive)

You can find many suitable images online by searching "red-cyan 3D". You can view them on the computer, or print them out and laminate them.