Azarhi Software: http://www.azarhi.com/Projects/DSW/
What a useful program: found in the comments to a hint on MacOSXHints, this Preference Pane allows applications to be triggered on disc mounts and unmounts.
Great for launching backup software, such as iBackup when I insert my 1GB USB stick, so one further click will copy all my most essential passwords and documents to the device.