Check out this post by Tim Heuer about some of the latest functionality just added to the http://maps.live.com This stuff is absolutely amazing, you have the ability to record a 3D tour of a saved collection and save it as a WMV file. He demonstrated a simple collection as well as posted it to Silverlight Streaming using a custom Encoder template.
Post: http://timheuer.com/blog/archive/2007/10/29/virtual-earth-3d-recording-windows-live-maps.aspx
Scott