ExtendScript Toolkit (ESTK) is an application used to edit and debug scripts targeting various applications in the Adobe Creative Suite.
While itself an application, ESTK is to a large degree implemented in ExtendScript. Extending ExtendScript Toolkit describes how to run or install scripts within the internal engine.
The ScriptRunner script invokes an OSX shell command without Terminal window.
The MakeFavorites script restores favorite folders whenever ESTK suffers from amnesia.
The ShowInFinder script adds a menu item to the Scripts panel's flyout menu.