We are currently developing a WebGL based virtual globe
It supports multiple image layers, elevation. It has many planned features. It is an open source project on GitHub (OpenWebGlobe/WebViewer). The plan is to create a high end SDK for new virtual globe applications.

If anyone is interested in participating in this project you can contact me.

A sceenshot of the current "preview" version:


And the movie:
http://www.youtube.com/watch?v=vvVhEpqHstE

More info is also available at: http://www.openwebglobe.org