Here is a scale model of the Solar System with a value of 3,474.8 km to 1 pixel. Lots of fun scrolling.
There was a pretty neat scale model of the Solar System at the University of Colorado at Boulder when I attended. I assume it is still there. I lived in the Kittridge Community my freshman year and Williams Village after that, so I frequently walked by the marker for the sun parked in front of the planetarium:
From there it extends to the other side of campus and the engineering center:
Along the way it passes a memorial for Ellison Onizuka, one of the Challenger astronauts. I imagine there is one for Kaplana Chawla now too, who was on the Columbia and did post-grad work at CU-Boulder.