Someone discovered a clean way to map chord progressions onto multidimensional geometrical spaces. It uses exactly the same kind of geometry that String Theory uses (no pun intended).

Here's the website:
http://silvertone.princeton.edu/~dmitri/

I read the theory behind it, and it seems pretty cool. It also comes with software where you can enter chord progressions (using a MIDI keyboard or just a regular computer keyboard) and then visually watch them move through multidimensional music space. It has pre-recorded movies of the software in action for a piece by Chopin and for Deep Purple.