Set global hotkey with Python 2.6
http://bytes.com/topic/python/answers/574341-how-create-global-hotkey
Looks like pyhook or wxPython for windows, and XLib for linux, or maybe keybinder for Gnome.
And if you were only listening for it while your program was active, Qt has something for it:
Respond to application-wide "hotkey" in Qt
Hope that helps.