OK, back here I was pondering on WTF Pirates Day was, well, I have a little bit more info.
It is on September 19th and there is one achievement involved and it is not part of the meta. Apparently you have to "Drink with the Dread Captain Demeza to join her crew during PiratesDay."
OK, I still don't know what is involved, so off to google it ...
... still here?
... back soon.
Well, apparently you need to talk to a pirate commoner in a capital city then take the option "I'd like to dress like a pirate". This will give you a "Corsair's Costume" buff which lasts for an hour.
Head on down to Booty Bay and talk to Dread Captain DeMeza who should be on the roof of the bank. (Even Bloodsail Admirals can do this apparently). This should convert the buff to a 12 hour "Dread Corsair" which persists through death and give you the achievement "The Captain's Booty"
The next day Brewfest starts, watch out for my guide coming to a Firefox 3.5 browser near you soon. (You do use Firefox don't you?)