This whole Core77 article about the design of Google Maps is pretty excellent. It’s a great breakdown of the insane challenges of building a map of the world. Beyond everything else, though, I found this especially shocking: “In recent months we have introduced a few more regional changes to our color palette adding 3D building shadows to indicate local time-of-day.” 3D building shadows … Who knew? (I can’t seem to track it down myself, but it’s in the screenshots on the article.)
Google Maps: Designing the Modern Atlas - Core77

Just in case you thought things couldn’t get any nerdier, here’s a good piece from Slate on what it takes to make a great map:
According to independent cartographers I spoke with, the big mapmaking corporations of the world employ type-positioning software, placing their map labels (names of cities, rivers, etc.) according to an algorithm. For example, preferred placement for city labels is generally to the upper right of the dot that indicates location. But if this spot is already occupied—by the label for a river, say, or by a state boundary line—the city label might be shifted over a few millimeters. Sometimes a town might get deleted entirely in favor of a highway shield or a time zone marker. The result is a rough draft of label placement, still in need of human refinement. Post-computer editing decisions are frequently outsourced—sometimes to India, where teams of cheap workers will hunt for obvious errors and messy label overlaps. The overall goal is often a quick and dirty turnaround, with cost and speed trumping excellence and elegance.
Who knew?
The best American wall map: David Imus’ “The Essential Geography of the United States of America” - Slate Magazine