ControlPlane is a very interesting automation tool for the Mac. It allows you to automatically carry out actions when certain conditions are met.
There are four concepts that need to be explained: Context, Evidence Sources, Rules, and Actions. First, the Context is the name that you give to a set of evidence sources. Say you want to create some automatic tasks for work and home, your contexts would be "work" and "home". Now, the evidence sources are what device on your computer or other variables trigger your actions. By default, AudioOutput, IP, Monitor, Power, Running Application, Time of Day and USB are enabled, but there are more sources available. In Rules, you set what has to happen in an evidence source for an action to be carried out. And finally, the actions, well, those are pretty self-explanatory. This might sound a little confusing, so let me explain it with an example. My Context is home, and I want the application to Speak some text when a certain monitor is connected to my Mac. All I need to do is select "Home" as my context, select "Monitor" in Evidence Sources, then select the monitor that I want in Rules, and then select "Speak Action" in rules and type in the text that I want. With the number of evidence sources, rules and actions available, you can accomplish lots of different great actions. It just takes some imagination and trial and error until you get it right.
ControlPlane runs at the Menubar and it supports Growl notifications.