gCAD3D is a free CAD app that provides the tools needed to create expertly rendered 3D models.
Did we mention it is free? You could spend a nice chunk of change on similar products, but this little freeware app packs tons of features. It is, however, displayed from a rather plain interface that is relatively easy to use, but we suggest reading through the documentation beforehand. gCAD3D includes multiple pre-rendered 3D models to choose from and use while you get yourself up to speed.
If you are new to 3D designing, then gCAD3D will be a great free starting point before branching out to more expensive apps.