When I recently read about something called "R-Screen" on Dassault Systemes blog "3D Perspectives", it reminded me of something I saw a couple of years ago.
R-Screen is a VR installation created with 3DVIA Virtools (VR pack) and is basically a rotating stereoscopic (rear-pro) screen that aligns towards the viewer based on head-tracking data. It allows to move around a virtual object which increases the feeling of immersion.
Something of similar purpose is Alias Research's "Boom Chameleon" from 1998/99 or so. You basically move a screen attached to a boom around it's center center like a window to the VR world. Nowadays with camera tracked markers, we have this even as Augmented Reality on portable devices! Interesting though how old these concepts are. Another demo shows a Mixed Reality example where objects are staged and affect a virtual scenario. This is called a Tangible Interface.
There are a few more (old but interesting) videos online from Alias Research (they take a while to load).