Wow. I'd tried World Wind in an earlier incarnation and had been frustrated by downloading problems. They've cleared those up. World Wind is the best use of computation I've seen in a long time.
It appears to set itself up as a MIME handler, because when you enter a worldwind: protocol in your browser, the application spins appropriately. This can be used to create animations (even before the promised arrival of scripting). It's a .NET app, too, and when I just pointed Visual Studio at it, I got a great big list of interfaces! Sweet! Direct output to videostream here we come!