Launch shell scripts via keyboard shortcut in Mac OS X
Solution 1:
In 10.6 Snow Leopard it's quite easy to add any command to the Services menu of each application (or specific applications), and then assign a keyboard shortcut.
Here on Super User, see Fast User Switching/Apple Menu? for an example that invokes some shell script.
Solution 2:
You can use Keyboard Maestro to launch an application or script from the keyboard. There is also IronAHK (AutoHotkey rewrite) which works under Mono, example:
^n::Run, /path/to/script.py
although make sure the script has sufficient execute permissions and a shebang line.
Solution 3:
You can also use automator to make a contextual menu invoked script.