The new feature called "content-aware image resizing" in Photoshop is amazing. There is a promotional video up on the Adobe site that's really fun to watch. For example, they make a Volkswagen bus more "economical" (mind you, while keeping the wheels round):
The technology behind it is based on research from an Isreali research group. That group put a video up on youtube in 2007 already:
It's a little more technical, but no less impressive, so all of you geeks who wonder how it actually works should watch this as well.
I can tell you one thing: I want this in Firefox's page resizing code. Sadly, I assume it is strictly patented and Adobe will probably have made sure to have some sort of exclusive deal on it.
Update: A commenter points out, there is an open source plugin for the GIMP that does content-aware resizing--already since 2007. Thank you, Gandalf!