Are you aware that there's such a thing as a 3D PDF? Most CAD packages can generate them, and Acrobat Reader can display them, although I'm not sure about the free version. It's a very cool way for many more people to be able to view a 3D rendering in 3D, rotating, zooming, without having to install a viewer. It seems to handle 3D renderings very well, too, without gigantic file sizes or tremendously slow redraws, though that might be more of a function of the generating software than Acrobat itself. But give it a whirl, assuming FreeCAD has it available as an output.
I use it with Altium (PCB layout software) at work all the time, and it's terrific. I used to hate trying to 3D render PCBs, but it works so quick and easy now I love it. When I show people a beautifully rendered PCB that's only half-way through the layout process, they're always blown away.
