A couple of months ago, I wrote a tutorial on Getting Started with 3D in Flash. It demonstrated how easy it is to use Papervision3D to produce a real time 3D interface within the Flash player. But so much more can be done with Papervision3D and other 3D engines for Flash. Here is a showcase of sites that take the 3D interface and environment to the next level.
This one is more of an experiment, but I included it because it looks incredible.