Virtual Earth
This documentation is no longer maintained. Please see the new GeoServer documentation at http://docs.geoserver.org
GeoServer is rapidly improving its ability to interact with Virtual Earth. As of version 1.5.2 we've got GeoRSS support, which Virtual Earth understands. There is a demo of virtual earth working with GeoServer included in all downloads as well.
In addition GeoWebCache now supports virtual earth tiles directly, rendered by GeoServer and cached by GeoWebCache for high performance. It is also in the process of being integrated directly with GeoServer, for now it is available as a drop in plugin, see the tutorial.