Earlier this year, I created a demo that showed how to synchronized video and animation in Silverlight and put it on my $2.95/month hosted dev server.  At the Mix in March, I actually demonstrated it in the Silverlight and Advertising session.  Watch the recording below - my demo starts at 59:49.
image

My plans are to migrate this demonstration to Silverlight 2, but in the meantime I decided to use the MSDN Code Gallery to share the code for the site: which is primarily JavaScript and XAML:

Media Overlay Designer on MSDN Code Gallery