There's a new product from zSpace, that based on the promo video, looks like it simulates a holographic screen and allows you to work interactively in simulated 3D space with the separate meshes and objects in your scene. Hard to say how effective this screen, pen and eyewear combo will be - stuff like will it work well under reasonably lit conditions, or will it really help you in production to work in 'true' 3D space. Works with Maya already though, but is only compatible on Windows. If you are wondering, the whole setup will set you back $6000USD.
Transform your PC into a zSpace virtual-holographic system.
» High-definition stereoscopic display with full resolution images rendered for each eye
» Lightweight passive eyewear
» Full motion parallax with sensors tracking the viewing angle of the user
» Uniquely designed stylus for managing all interactions in 3D space
» Development platform for creating new applications and integrating new input devices
» zStation monitor - 24 inch HD LCD (1080p120Hz) with built-in tracking sensors
» Laser stylus with 3-buttons and integrated infrared LED
» Polarized passive 3D eyewear
» 1-year standard warranty with option for 3-year extended program
» zSpace SDK for software developers
» zSpace Maya Plug-in (available to licensed users of Autodesk Maya)
» PC with Microsoft Windows 7 (32/64 bit) with a stereo capable graphics card supprting DVI-D and/or DP ports