This scale model of the Sun and planets is inspired by http://www.thingiverse.com/thing:1430614. I created a new model and printed it in 2 colors.
Mercury, the planet closest to the Sun, is on the left and Neptune is on the right side. The Sun itself is on the back. You can also see the Moon, close to the Earth. The moons of other planets are not shown, there are to many of them in our solar system.
The width of the model is 20 cm and has a scale of 1 : 2,500,000,000. The Sun would be 55.7 cm on this scale, so only a small part of it can be shown. Only the size of the planets and Sun are at scale. Distances between the planets are so huge, they can't be show using this scale. The thickness of the rings of Saturn are also not at scale, they are very very thin. I just made it thick enough to make it printable. The distance between the Earth and Moon at this scale is 15.4 cm, to large for this model, so I had to reduce it.
The rings of Saturn are a combination of the A and B ring, these are the main rings. The Cassini division between these rings is not shown. This gab between the rings is to small to make it printable. Maybe the rings are already tricky to print, but it worked in my case.
My printer can only print using one color. I started printing in blue and changed the color to white at the right moment. This gives a very nice result in my opinion. It took my printer 12 hours to print.
There is also a smaller model (10 cm), with a scale of 1 : 5,000,000,000.
solarsystem.stl (20 cm model with text in English)
solarsystem-NL.stl (20 cm model with text in Dutch, this one is shown here)
solarsystem-small.stl (10 cm model)
The rings of Saturn are quite delicate in the small (10 cm) model. I added a new one with a ring thickness of 1.5 mm, which must be easier to print. (solarsystem-small-EN-ring.stl)