Google Calendar - When an event is continuing to the next week, they give you a little arrow.
/via Pierre Valade
Skype 5.0 for Mac - Displays an arrow next to a person’s mood message. When clicking on the arrow, all links will be opened at the same time.
Mac OS X - When searching in the help menu of an app, the menu relevant to the result is pulled down with a blue moving arrow pointing at the menu item.
/via Stephen Litt Belch