Task panes, also known as Action Panels, are user interface elements seen in a number of mainstream applications, both on web and desktop platforms. They are mostly used in cases when there are too many items and actions to be organized in a menu or a toolbar. They are most commonly implemented in the form of a panel with organized groups of related actions.
Microsoft Office 2003 and earlier versions have been filled with task panes, though in their modern versions such as Microsoft Office 2007 and Microsoft Office 2010, ribbon is the most prominent UX pattern.
Here are several examples of task panes found in today's applications:
Start your Expression Blend 4 and then select New project... ...