Here's an example: I want to say the word Widgets, and have the Dashboard show (or hide if it's showing). To do this, I make an AppleScript with this code:
on run
try
tell application "System Events" to key code 111 --F12
end try
end run
Save the script in the Speakable Items folder with the name Widgets, and with the extension hidden. Now when you have Speakable Items enabled (I have mine set to listen continuously) and say the word Widgets, the Dashboard will show or hide. You enable/disable Speakable Items in the Speech System Preferences panel.

