Here are some papercraft planets.
Cubes
Each pattern will give you a 4″ cube when assembled (Saturn’s rings are to scale, and are a little more than 9″ across).
To-Scale Planets
Please note that the to-scale Jupiter and Saturn require tabloid (11×17″) paper, because they’re just that big. If your home (or work!) printer can’t handle that, you may need to visit a professional copy-and-print shop.