If you have photoshop CS6 extended, there's a fine 3d engine in it now. It's not as powerful as most of the real 3d software (like blender or 3dsmax), definitly not map-orented and not that easy to use at first, but i think you can already make some fine 3d work just with that. I'm currently in process of learning how to use it well, and the results i got are satisfying for now, the "convert layer to 3d form" is actually pretty handy to shape planets and simple editable forms. It all depend on what you wish to achieve in the end.