Inspiration and code from soulsolutions.com blog posts on Virtual Earth and Deep Zoom Part 1, Part 2 and Part 3.
Other code from silverlightearth.com and Geoquery 2008. Updated for Silverlight 2.0 Release Candidate 0.

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Silverlight 2.0 (Deep Zoom) Earth viewer requires Microsoft Silverlight 2.0

SilverlightEarth.com is a Microsoft Silverlight 2.0 (Deep Zoom) map viewer utilizing map image tiles from different sources including Virtual Earth, Google Maps, Yahoo Maps, as well as NASA Blue Marble and Open Street Maps.