Algodoo

If you want to create one, It's important to say that between each step of the gravity/speed manipulation, you have to wait a minimum of 3 to 5 minutes to create a good effect. The longer you wait, the better your solar system will be.

1- Create a new scene where you put off the gravity pull and the air effect (the 2 squares). Put the sky black and put off the clouds.
2- Create a big circle that you paint bright yellow. Attach a hinge to the center to lock it to the background. Here's an image of the size of the circle at 1.00 zoom:
3- Make 8 circles of 8 different sizes. Copy each of them like that (from the smallest to the biggest):

Size 1: 200
Size 2: 35
Size 3: 20
Size 4: 10
Size 5: 5
Size 6: 4
Size 7: 2
Size 8: 1
4- Put 12 attraction and max friction to the sun and put 10 rpm and infinite force to the hinge.
5- Start the animation. All the balls will collide to the sun and begin to turn. All the netx steps have to be separated with a minimum of 3 to 5 minutes of waiting to bring a good effect.
6- Slowly rise the rpm of the hinge by 2 rpm and a waiting to bring it to 18 rpm. After that, slowly descend the attraction of the sun by 0.5 and a waiting to bring it to 10.
7- Slowly rise the rpm of the hinge like in the number 6. All the system should stabilised around 62 rpm.
8- Slowly descend the attraction of the sun to bring it to 8.6.
9- Put textures on the planets (marbles textures are better).
10- You have your solar system.

When your solar system will be stable, it will have many elliptic revolution. If you do nothing, several planets will go out of the system forever. To (naturally) remedy that. Put the animation to pause, create 50 of the smallest rounds and 20 of the next size really close to the sun and continue the animation. The spread of this little balls will collide on the planets and help them to have a round revolution.