As I watched Steve Jobs present Apple's iPhone, I knew that I had heard about multi-touch interfaces before. Take a look at this multi-touch display, created by a design team from New York University Media Research lab.
Update 08-Feb-2007: See an additional, very cool video demo of Multi-Touch 2 in use in a variety of settings and applications, with multiple operators. End update.
Apple claims to have patented their interface out the wazoo, but this is the one you want. On your desk... top.
If you've seen the 2002 movie Minority Report, directed by Stephen Spielberg from the Philip K. Dick short story, you've seen some of these moves. In the picture shown below, Tom Cruise moves material and reorients it on the wired glove interface display with a multi-touch gesture.
(Minority Report multi-touch interface)
In the next example, we see Jeff Han moving material and orienting it with a similar movement.
(Multi-touch screen gestures)
Here's Steve Jobs doing the Apple iPhone version - they call it "the pinch."
("The pinch" multi-touch from Jobs' iPhone demo)
I almost forgot another unique multi-touch screen; the Khronos Projector, created by Alvaro Cassinelli. It projects prerecorded video of a scene over time onto a flexible screen. As you push on the screen, your push is noted by the interface and the video on the "pushed spot" goes back in time. In the picture, a push on a daylight picture of a city goes back to a nighttime view. And yes, you can push on multiple places at once.