There was a requirement where I have to plot the office locations of my client in SharePoint using SharePoint Designer from a SharePoint List. I have googled around for some time and found couple of interesting articles which helped me a lot to plot the maps.
http://blogs.msdn.com/sharepointdesigner/archive/2007/05/23/plotting-your-data-using-virtual-earth.aspx
http://geocoder.us/demo.cgi
http://blogs.msdn.com/sharepointdesigner/archive/2007/06/15/how-to-integrate-virtual-earth-maps-with-a-sharepoint-list.aspx
http://www.wssdemo.com/Blog/archive/2008/09/05/sharepoint-virtual-earth-web-part-without-deploying-any-server-code.aspx
http://blogs.msdn.com/sharepointdesigner/archive/2008/12/05/creating-restful-mashups-using-spd-2007-part-1.aspx
http://msdn.microsoft.com/en-us/library/bb259691.aspx