Perhaps you saw my MIX presentation of Virtual Earth in Silverlight. If not, check it out. In the meantime, you can check out Virtual Earth in Silverlight as the backdrop and interface respectively for the game Destroy All Invaders, by Andy Beaulieu. I found this link off of the Public Sector Developer Weblog.
It's classic. Using your mouse to direct a helicopter and the CTRL button to accelerate it, you fly over different areas of the US with Virtual Earth's Oblique Imagery (aka Bird's Eye) while shooting down UFOs. You can play over Upstate New York; The Statue of Liberty; Universal Studios, Orlando; Las Vegas, NV; Los Angeles, CA; Philadelphia, PA; Microsoft Campus, Redmond, WA; or Hollywood, CA. I love this. It's built with Silverlight 2.0 and The Virtual Earth tile set. Great stuff Andy!