In part 2 of this series, Derek Chan shows how to integrate the Mappoint Web Service platform on a Virtual Earth map.
http://www.viawindowslive.com/Articles/VirtualEarth/InvokingserversidecodeusingAJAXPart2.aspx
If you recall part 1 introduced the concepts of using a httphandler to communicate between server side code and Virtual Earth.
http://www.viawindowslive.com/Articles/VirtualEarth/InvokingserversidecodeusingAJAX.aspx
As usual the full source code is available for download. Great work Derek!