Have you seen the Deep Zoom example with the Hard Rock Cafe artifacts? It's pretty darn cool. If you don't have Silverlight and would like to see why it's cool, there's a video on the Mix blog. But I love the zooming into Virtual Earth example I was just sent. It's a CodePlex project, so you can be part of it. It can take a while to load so be patient. I showed it to someone who said that Google Earth did that, but requires downloading and installing an application. If you already have Silverlight, you don't need anything else to use this. I like that.