Microsoft's Vermeer holographic display puts the hologram out in real space, where you can see it without glasses. And you can interact with it.
(Vermeer 3D Volumetric Touchable Display)
The Vermeer display is similar to the mirascope device that uses parabolic mirrors sandwiched together. Microsoft has placed a light field projector that can render 3,000 imgages per second between the mirrors; it can project an image at 15 frames per second for 192 different points of view.
Oh, did we mention that you can mess with it? 'Cause you can. Since there's no glass or spinning parts or anything mechanical surrounding the hologram itself, you can poke and prod it as much as you like. And when you do, the hologram can react. One of the crazier things about mirascopes is that since they're just mirrors, they work both ways: putting a real object inside projects a virtual object outside, and at the same time, putting a real object outside will cause a virtual projection of that object to pop up inside the mirascope itself. Microsoft has taken advantage of this, and by putting an IR illuminator and tracking camera inside the mirascope, they can track the virtual image of your hand as it interacts with the virtual image of an object.
Most readers will recall this scene from the original Star Wars film from 1977:
(Help me, Obiwan Kenobi - you're my only hope)
However, this idea has been used in sf for quite a while. Here's a quote from the 1928 novel Crashing Suns, by Edmond Hamilton:
Abruptly I was aroused from my musings by the sharp ringing of a bell at my elbow. "The telestereo," I said to Hal Kur. "Take the controls." As he did so I stepped over to the telestereo's glass disk, inset in the room's floor, and touched a switch beside it. Instantly there appeared standing upon the disk, the image of a man in the blue and white robe of the Supreme Council, a lifesize and moving and stereoscopically perfect image, flashed across the void of space to my apparatus by means of etheric vibrations.
(Read more about Hamilton's telestereo)