Here is the first map I ever published online, a visualization of what locations people were looking at on Google Maps on April 6, 2005. This was right after Google Maps added satellite imagery. Here's the official blog post about the visualization; the published image is gone, good thing archive.org has it.
I wince to see the ugly stretched projection; I didn't know anything about maps, so I just plotted longitude and latitude as X/Y axes. (Cartographers call this Plate Carrée; it's generally a sign the mapper is clueless.) The greyscale histogram is not particularly good, although in my defense the original unscaled PNG was nicer. I think the whole thing started as a fun project to learn Sawzall, Google's 20% time in action.