StackPanels are one of the derived Panel Classes, and is commonly used in many examples and sample code for the Windows Phone 7. It is a good looking way to present child elements in either a horizontal or vertical manner. Buttons, Bing Maps, Calendars, progress bars, all look great in a vertical stack panel.
The StackPanel is one of the Panel Base Classes available on the Windows Phone 7.
In the simple example that is presented in the video, you can see the ease of use.
Code (you can cut and paste):
<ProgressBar Value="50" Height="30" />
Reference: Developing Windows Applications with Microsoft Visual Studio 2010 and internet sites as indicated.