Marc Schweigert has put together a CodePlex project to support Intellisense for the Virtual Earth Map Control in Visual Studio 2008.  VS2008 JavaScript Intellisense provides an interactive display showing functions and parameters with drop-down lists and documentation as you code.

 

The project is just starting and needs community support, if you are interested, feel free to join and contribute to the project.  Check out Marc's Blog for more details.