It is not longer necessary to spend thousands of dollars on a large touch screen or multi-touch display.  Now all you need is a Wiimote, bluetooth, and a couple infrared lights like on keychains.  This is a super easy thing to wire up and can really provide a nicely calibrated display with up to 4 simultaneous points of touch.  You can hook up a projector and utilize the area like in minority report.  This software also works within the Windows environment to allow full interactivity with any program, not just specialized programs.

The software is written by Johnny Lee from Carnegie Mellon University, and is open source and available at this link.  The original article which also covers step by step instructions and calibration is here.