This Solar System Orrery by Jeroen Gommers provides a top-down view of the solar system so you can observe how the planets move relative to each other.
The orbits and size of the planets has been squashed to make it fit onto the screen, but their relative motion are accurate. In reality their orbits are elliptical as well, rather than circular as shown in this model.
Drag any planet around to see how the other planets move. The simulation includes the dwarf planets as well as the 8 major planets.
Use this in class to show how the inner planets complete their orbits relatively quickly, whilst the outer planets can take many years to do the same trip.
If you like this, then check out Space Resources for your Interactive Whiteboard which has more interactive resources like this.