I got a nice note from John Yunker:
While most country codes are fairly obvious, such as DE for Germany and JP for Japan, many others are not so obvious. For example, Serbia is RS and Sri Lanka is LK.
Last year, I designed a map that illustrates the world's 245 ccTLDs in a way that is both useful and informative. Each country code is sized according to the population of the given country/territory. China and India were sized down by 30% to accommodate the layout.
It is available as a 24 x 26 poster ($30).