AppleScript
AppleScript is a scripting language created by Apple to control application behavior. A script can speak the time every half hour. A script can open iPhoto, search for all photos named "(nnn) party.jpg", and rename them to "Party nnn.jpg". It can automatically save the last fifty Firefox tabs into a tab group (if like me you open a bunch of tabs at a time).
Note:
defaults write /Applications/SomeApplication.app/Contents/Info NSAppleScriptEnabled -bool YES
enables AppleScript support for SomeApplication.app. See Mac OS X Hints.
