The reason you don't see realistic models very often is because objects we use as for reference (planets) are too tiny compared to the space between them. Earth would be nothing more than a speck of dust in a football sized model.

That said, here's a model with proper proportions of distance: http://www.solarsystemscope.com/ - Flash required, click anywhere, click on the gear icon to the left to select realistic size and model. Zoom slider is to the right. Note, the sizes and colors are wrong, most planets would be pretty much invisible in a realistic model.

Here's a neat non-interactive one from NASA: http://space.jpl.nasa.gov/