On this date in 1967 the Principality of Sealand was founded, or the land was first occupied or the permanent residency of its future ruler began or however you want to characterize it. Their official website has a history page that reports part of the micro-nation's history:
After WWII ended, the troops were withdrawn from all bases by the British Admiralty. None of them was ever used by the United Kingdom again, leaving the forts deserted and abandoned. Except for the aforementioned fortress, the bases were subsequently pulled down. This resulted in the portentous uniqueness of the fortress. Fort Roughs Tower, situated at the high seas, had been deserted and abandoned, res derelicta and terra nullius. From a legal point of view, it therefore constituted extra-national territory.
The Birth of Sealand
This paved the way for occupation. On 2 September 1967, former English major Paddy Roy Bates formally occupied the island and settled there with his family. After intensive discussions with skillful English lawyers, Roy Bates proclaimed the island his own state. Claiming jus gentium, he bestowed upon himself the title of Prince and the title of Princess to his wife and subsequently made the state the Principality of Sealand. Roy Bates, henceforth Roy of Sealand, exerted state authority on the island and thus was an absolute sovereign. The royal family and other persons that have declared loyalty to Sealand have occupied Sealand ever since.
About.com's Geography page claims The Principality of Sealand does not qualify as a legitimate country. Spoilsports! There's an interview with the Prince of Sealand on youtube:
It includes some video of the island itself.
Recent news includes the sad decision that Sealand will not be hosting the World Cup because of concern about losing things (like balls. and players.) over the side during matches, despite Sealand's assurances that helicopters stand at the ready to perform speedy rescue operations. Sealand is for sale; interested? Sealand has a Facebook page that appears to be updated with some regularity.