Microsoft MapCruncher is a new tool from Microsoft Research Labs that lets you play around with the Virtual Earth Satellite Imagery. For instance, you can add your own aerial photography to Virtual earth, create a route map with Visio from scratch and place it over Virtual Earth just like you add a Photoshop layer.
If you look at MapCruncher features and capabilities more closely, they look so similar to what Sketchup-Google Earth is doing - Open Google Earth, capture a snapshot and export it to Sketchup, create 3D drawing and put it back in Google Earth. Mapcruncher doesn't do 3D modelling yet but apart from 3D, it does everything else and even more.
Say, if Virtual Earth is not showing high resolution pictures of your hometown, you can add them on your own. Or if the existing maps don't zoom to the street level, you can take the invitiative and create the map yourself. Mapcruncher also generates the code for embedding the map mashup on other websites. The other advantage of using Mapcruncher is that it accepts overlay data in all graphic formats and even PDF.
Download Microsoft Mapcruncher