“Seam carving” gracefully resizes images without apparent distortion and still includes the important elements of a picture. You can reduce or expand a photo horizontally or vertically and the photo would still look natural; no scaling, no cropping and no stretching. I can try to explain it to you in so many words but the best way to understand the concept and what it can do is to watch the YouTube video here (nerdy voice and language, but the video will convince you that it is amazing).
That technology has since evolved into an application called Liquid Resize which has been acquired by onOne Software (bless them!). It is now ready to be released as a public beta, for FREE (double bless them!!) and will come out later this month.
A plug-in version for Photoshop is due in the middle of this year, and that will no longer be free of course.
Go watch the video, buddy, the guys who thought this up are geniuses.