It's hard to top Microsoft Surface, but the brains at Microsoft Research (with help from MS Hardware) certainly did with SecondLight. SecondLight is a variation on the Microsoft Surface computer, the twist is that it can actually project a second image through the first image, which can land on a sheet of paper, a plastic sheet, or anything else semi-transparent that you want to use as a make shift secondary (or third, fourth, fifth) display. Those displays can also have their own multitouch capabilities in the air.
So what does this mean? It means a doctor can use a sheet of paper to dynamically 'cut through' a 3D MRI, or you could even scoop up windows on a surface computer and then interact with them on this lightweight display without altering the original Surface image. We just showed SecondLight at the MSR keynote but last night I got a few minutes with Steve Hodges, Alex Butler, and Shahram Izadi from the SecondLight team and they walked us through how it works. I apologize for how horrible I sound, I lost my voice the day before. Also, we couldn't turn the lights on so it's a little dark.