The best ideas are obvious in retrospect
This is one of the coolest — and simplest — image-processing ideas I’ve seen in a long while. (It will even be of interest to non-geeks, as I’ve just demonstrated by showing it to Emily: “Whoah! That’s impossible!!”)
They call it “seam carving:” it’s a technique for allowing resizing of images by removing the least visually significant parts of the image first — or enlarging by adding pixels where they’re least likely to be noticed. The idea is so computationally simple that it’s difficult to believe nobody’s thought of it before, but the results are so nifty that if anyone had thought of it before now, it’d be ubiquitous already.
Make sure you watch to the end, when they start demonstrating variations on the technique that allow you to (for example) seamlessly remove individual elements from an image. The paper describing the technique is available here.
I await the Photoshop filter with great anticipation.