then you need to go read Spencer's Blog.  I chatted with him all too briefly before the last Austin IASA meeting and we discussed some of the things he's doing with Virtual Earth and his GPS information.  Get the full information over at his site - http://spencerwilliams.net/blog/ there's a lot of great observations about what he's doing and what can be done with the platform!

(updated to correct my overenthusiastic spell checker.)