My colleague Matt sent round a link the other day to a Stanford paper on Light Field Photography. These geniuses have built a plenoptic hand held camera that takes a 4D light field picture in a single exposure. It is all very technical, but it essentially means you can re-focus a single picture to different depths in post-production.
Rather than duplicate the images from the site here, why not click through and check it out yourself. There is a sequence of 5 images of a crowd on the homepage here. On the gallery page, there are a number of videos of the images being changed right before your eyes.
For the technically inclined, there is also a copy of the paper there too: Light Field Photography with a Hand-held Plenoptic Camera.
