Tim Heuer has a great blog post on the new NotificationWindow class for Silverlight 4 Out-Of-Browser applications. This class allows you to create notifications or 'Toast' for your Out-Of-Browser applications when you need to provided helpful information to the user as they are interacting with the application.

Tim provides great visuals for the notification window in his sample application, and I decided to leverage his sample to explore things myself and created a style that maps nicely with the default Silverlight control styles. My sample project can be found here and the visuals can be seen below...