NASA Web WorldWind
The WorldWind Explorer was created by Bruce Schubert and is powered by ESA-NASA Web WorldWind which provides the 3D Earth visualization with WMS maps, imagery and terrain.
WorldWind is different from a 3D globe like Google Earth because it is not an application. Instead, it is an SDK (software development kit) that software engineers can use to build their own applications. WorldWind is a free, open source API for a virtual globe. WorldWind allows developers to quickly and easily create interactive visualizations of 3D globe, map and geographical information. Organizations around the world use WorldWind to monitor weather patterns, visualize cities and terrain, track vehicle movement, analyze geospatial data and educate humanity about the Earth.
The NASA WorldWind Java SDK (WWJ) is for building cross-platform 3D geospatial desktop applications in Java.
With WorldWind handling the hard work of visualizing geographic data (generating terrain from elevation models, selecting and displaying images from imagery servers, etc), software engineers are free to focus on solving the problems specific to their own domains and more easily building whatever geospatial applications they choose.