Mac OS X: While it's no AutoHotkey, Apptivate is a simple way to assign keyboard shortcuts to applications on a Mac. This means you can run AppleScripts with nothing more than a keystroke, too.
Apptivate is an incredibly simple application that sits in your menubar and lets you add a keyboard shortcut to launch any application installed on your Mac (assuming that keyboard shortcut isn't already taken). This is really handy for switching between and launching applications quickly, but what's really exciting is that you have the option of running an AppleScript via a keyboard shortcut. If you want to do this, all you have to do is save your AppleScript as an application and add it to Apptivate. Once you've chosen your keyboard shortcut, you'll be able to run it very easily from the comfort of your keyboard.
Apptivate is available right now in the Mac App Store for $4.
Apptivate ($4 in the Mac App Store).