R2012a and earlier instructions: Type prefdir on the command line. Go to the folder it gives. Then copy the file shortcuts.xml from the prefsdir of the source computer to the prefsdir folder of the target computer.
[EDIT - UPDATE FOR COPYING EARLIER SHORTCUTS TO VERSION R2012b]
Apparently the new shortcuts XML file MUST be called shortcuts_2.xml.
All my shortcuts are 1 (sometimes 2) lines which point at script m files. These m files reside in a single directory which is on my MATLAB path. I can then play around with copying the shortcut information from prefdir, or just recreate them as I go.