Was messing around with this a few days ago, got an okay list going, figure I may as well stick it up here.
Note that in general my attitude was "this is a first pass that I was trying to fill; if someone can think of a better example for a particular length, then please suggest it. If you have criticism of an example, please speak up--so far these discussions have led to better examples."
10^-15 m: Size of a Proton
10^-14 m: Size of a large nucleus (like Uranium)
10^-13 m: ?
10^-12 m: ?
10^-11 m: ?
10^-10 m: Size of basically every atom (heavier atoms pull their electrons in more, apparently)
10^-9 m: Pentacene (the molecule that was photographed recently)
10^-8 m: Small viruses
10^-7 m: HIV
10^-6 m: E. Coli Bacteria
10^-5 m: Length of a human DNA chromosome when laid out on a dish
10^-4 m: Particle of (white) Flour
10^-3 m: Flea
10^-2 m: Human fingernail
10^-1 m: Diameter of a CD
10^0 m: Height of a 5-year-old child
10^1 m: Height of a telephone pole
10^2 m: Length of a football field/pitch (both kinds of football)
10^3 m: World Trade Center towers if they were stacked on top of each other
10^4 m: Width of San Francisco
10^5 m: Most sprawling cities in the world, like Dallas-Fortworth-Arlington, and the New York metro area.
10^6 m: Length of Italy
10^7 m: Earth
10^8 m: Saturn
10^9 m: Sun
10^10 m: Some larger stars (like Beta Centauri)
10^11 m: Distance from the Sun to Venus
10^12 m: Distance from the Sun to Jupiter
10^13 m: Distance from Neptune to Pluto when they're on opposite sides of the sun
10^14: Distance from the Sun to "90377 Sedna" (a Planetoid like Pluto except it's about 15x as far away).
10^15 m: Radius of the Stingray Nebula (Okay, could definitely still find a better example here)
10^16 m: Gravitational Boundary of our Solar System (furthest distance comets can travel and still keep rotating the sun)
10^17 m: Distance between the Sun and most nearby stars (Sirius, etc).
10^18 m: Radius of the average Globular Cluster (bunches of stars, usually close to the center of the galaxy)
10^19 m: Thickness of the Milky Way Galaxy
10^20 m: Diameter of an average sized Galaxy
10^21 m: Diameter of the Milky Way Galaxy
Some videos and images that I inevitably bumped into while on my search (not that they really helped me any, but they are really cool looking)...
http://www.youtube.com/watch?v=9BjHvwSvpOwhttp://sizeofworldse.ytmnd.com/
