O3D - Open source Javascript 3d Engine

“What is O3D?
O3D is an open-source web API for creating rich, interactive 3D applications in the browser. This API is shared at an early stage as part of a conversation with the broader developer community about establishing an open web standard for 3D graphics.”

“Code: O3D extends application JavaScript code with an API for 3D graphics. It uses standard JavaScript event processing and callback methods.”

http://code.google.com/apis/o3d/