ISO standard 3166 lists official country short names and their associated two-letter country codes.
These are used (for example) for the 2 letter ccTLD names (country-specific domains such as .NZ). You might be able to find the list on a GNU/Linux system in /usr/share/zoneinfo/iso3166.tab.
There was a minor kerfuffle in 2004(?) when some ISO staffer proposed charging royalties to anyone using the 2-letter codes in their business, although those plans were quickly dropped following the predictable outcry.
No other page links to iso-3166 yet.
