This ingenious website made by David Paliwoda shows how far Mars is from Earth in a metric all us Internet lovers understand: pixels. If Earth was a 100 pixels wide, how far would Mars be? To start off, the moon would be 3000 pixels away (and 27 pixels wide). Mars?
My favourite demonstration of these distances is the scale model of the solar system in the Smithsonian in Washington DC.
Over the distance like a kilometre or so, they have the planets 3d printed in these glass cube things (if I remember right, mars is just a single tiny bubble on the glass cube), then at the end is the sun as a big (relatively) golden ball.