For no particular reason; just that it's a cool chart:
Following the link from the former, it looks like it was put together by Bill Rankin, who is pursuing a dual Ph.D., in the history of science and architecture at Harvard, and who enjoys graphic design and cartography in his spare time. Either this guy has 72 hour days and no need for sleep, or I am even more inferior than I thought, but never mind that. The above chart appears here, on his hobby site, Radical Cartography. From the home page, follow PROJECTS → BROWSE BY GEOGRAPHY → THE WORLD → POPULATION to get there, if the "here" link doesn't work. Be advised that if your tastes for nerd eye candy are at all like mine, you risk losing the rest of the day.
[Added] I am by no means close to being done browsing this site, but I wanted to note that I particularly liked the "Underdevelopment" map of Manhattan.
[Added3] A new word! endorheic, a geographical term which means an internal basin that does not drain outwardly. Not all water, it turns out, ends up in the sea. Who knew? From the Physical Geography page.
[Added4] World railways. Be sure to download the full-size image.
[Added5] U.S. Empire.
[Added6] From a link in the Research Candy section of Bill's academic page: "graph of the development of the US patent system." (PDF) Note especially the one titled "Patent Activity (per million population)."
[Added7] From same section: "graph of US construction activity, 1915–1960."
[Added8] Back to the RadCart site: "Place-Name Etymology."