Add a map element for "Date". Many maps need a date on them to show when they were made or last updated. Similar to the north arrow or scale bar, I think a Date element tied to the computer clock would be useful. So when I add the date and print the map one day, then open it and make changes the next day, the date has changed automatically because the date is tied to the computer's date.
This idea has been merged with Auto Text Date (etc) on ArcMap Layout.