Cuttlefish
Cuttlefish allows you to create events that only happen under certain circumstances. For example, I like to keep my audio muted as I don’t like system sound to be played out to me. However, I have Cuttlefish setup to automatically un-mute my sound when I open Rhythmbox or Totem Movie Player. Then when I exit either application, the sound is muted again. Cuttlefish is very powerful in what it can do, you can do things like opening your browser when Ubuntu connects to your wireless LAN, or automatically lock your screen when a USB stick is unplugged (this is a great idea for computers in public places like in work).
