Aurora is a design concept for a 3D browser by Adaptive Path who are working in partnership with Mozilla Labs and have presented a mock up of what a future browsing experience might look like.  So, it's not a real product, or even a product in development, but it looks cool nevertheless.

I have seen this sort of thing before, there are a few 3D browsers either in the concept stages or early development stages, although most fail to go anywhere.

In the case of Aurora we seem to be seeing more of a 3D desktop experience (where browsing is a just one part).  This would seem to make any such project that much more difficult because other applications (and operating systems) would need to cooperate - and the world is still waiting for the contextual desktop that Microsoft had hoped to include in Vista.

All that said, I have to say that it looks interesting.  I hope this goes somewhere.