Here's a bit of technology that could become a useful tool for photo retouchers. Researchers have developed a new way to change the shape of an image without distorting important elements in the picture. Called seam carving, the technique looks for patterns that can be easily compressed or eliminated while preserving the content of the overall image.
It's easy to understand when you see it in action. I first saw seam carving demonstrated in this CNET video. A quick Web search turned up the site of Dr. Ariel Shamir, who has posted a paper about the technique and another video.
Finally, here's a demo site where you can try it yourself with your own images.