I came across this trick by accident and it sounded so clever I had to try it. It's a way of creating an apparently infinite depth of focus in macro images, where the DOF is usually pretty limited. You take several images, focussing progressively from front to back (or back to front) and then "stack" them to combined the in-focus parts from each image. It's very easy to do this in Photoshop - here is a good tutorial on the process: http://photo.tutsplus.com/articles/post-processing-articles/focus-stacking-made-easy-with-photoshop/.
The first seven photos are the raw images - you can see how the focus shifts. The last image is the result of stacking them using the procedure given in that tutorial - note how every part is in focus! There are a few tiny glitches, but they're not really noticeable.
For this to work well, the exposure and aperture need to be the same between shots, and you need a tripod to ensure the camera doesn't move.