VPT Mapping Software
VPT is a free multipurpose realtime projection sofware tool for Mac and Windows created by HC Gilje.
Among other things it can be used for projecting video on complex forms, adapt a projection to a particular space/surface, combine recorded and live footage, for multiscreen HD playback, for interactive installations using sensors or camera tracking. VPT has become a popular tool for theatre and installation use.
You can get more info or download the software here.