3D Stereograms

Can you see the image below in 3D or does this just give you a migraine? 3D Wonderstuff has pages of amazing headache material like this - they honestly have some of the best ones (as far as really "popping" online. Their animations take a little more effort, but are very cool

If you're more interested in photo-realism, Ledametrix uses special mountings of identical cameras to produce 3D images that are quite 3D. Check out his galleries and you might just want to be picking up a second camera.