Although the country code .SU (Soviet Union) refuses to die, .YU (Yugoslavia) is now history.
As the ICANN blog notes:
With the transition of Serbia and Montenegro to using .RS and .ME comes the task of migrating users from the .YU domain. As we have talked about before, ICANN uses an international standard for determining country codes for use on the Internet. This standard, known as ISO 3166-1, indicates when new countries codes are created, changed or removed. As Yugoslavia, the predecessor country to Serbia and Montenegro, is now a piece of history so too is its YU country code.
Awhile back I wrote about the addition of .ME and the potential challenges it poses.
Also (possibly) on the horizon is a domain name for Kosovo. Much resistance must be overcome (namely Russia) before this domain becomes a reality, but I imagine it will within the next two years.
Finally, .KP for North Korea was also recently approved by ICANN as an official country country code.
To keep track of all 245 country code top-level-domains (ccTLDs), check out our new Country Codes of the World map. It even includes .KP.