James Fee noted this NASA program that competes with Google Earth.

Many of our clients can't use Google Earth because of its license and I'’m sure others will begin to run into that problem. World Wind might just be the solution and we'll see how well it handles Shapefiles.

I noted on the World Wind website that they are using USGS Quads for the United States, which might put them a leg up on Google, with gets pretty fuzzy in rural areas. I'm downloading it now and am going to try it out.