Sketchfab is online 3D sharing system for view only, just like Youtube for the video.
As you can see, it can be embeded in a web page, and use webGL standard.
The model can be uploaded directly from some 3D soft like Sketchup, 3Dmax, C4D, Blender... with a plugin (not MoI :( ) or via the web undersantding 25 3D format (polygonal, so no 3DM :( again).