From expensive-things-I'll-probably-never-afford file:

Chad Dyner, an MIT graduate student, has invented something he calls the "Heliodiplay". It's a display device that displays images in thin air, without the need for a projection screen or other refractive surface. The working prototype can display a 27" image at 1024x768 resolution, although his company's web page states that they plan to build a model capable of a 150" inch image.

What's even cooler is that the display works like a touchscreen -- you can reach into the display and manipulate visual elements by grabbing them.

I have no idea how this could possibly work, but it apparently does. Check out http://www.io2technology.com for more information.

With this sort of technology in the pipleline, can the the giant rotating planet display from Return of the Jedi be far off (hopefully not -- and at a much higher resolution!)