OK found one.
Some of you guys are about to be tilted because you won't be able to do it, but inside of this pic is a little 3D doggy...
My best advice for seeing it:
Click on this small image and use the larger one.
Don't look at it, look through it.
Don't look at one part, look at all of it.
Blur your eyes a little and the 3D image becomes crystal clear.
Once you're locked in, you can move your head left and right slightly and the dog moves in this 3d 'world'
Even though I've done this a hundred times, sometimes it still takes a few seconds to get into the 3D world, but you'll know once you're there.
Good luck!
Edit: They're called sterograms.