Here's the source to the WriteableBitmap sample I showed at Mix.  The sample uses WriteableBitmap to take a "snapshot" of the running video to make a thumbnail.  Click on the image below to run the sample.  When running the sample, click on the running video to create a thumbnail.  You can find the video for this sample here.

 

 

WriteableBitmap Image

 

 

The demo shows the following new Silverlight 3 features:

 

·         WriteableBitmap

·         WrapPanel (new SDK control)