September 19 is 'Talk Like a Pirate Day'. This is the only invented holiday which I heartily endorse. This is partially because it wasn't invented by a candy, flower or greeting card company but it's also because I think we should all be encouraged to spend at least one day a year acting goofy and talking funny.
There are several official web sites for 'Talk Like a Pirate Day' but the most official-looking one is here. While they are pushing a book, they also link to pictures of people observing the day.
If I were in the U.S., and had access to a variety of friends who could understand the concept, I'd definitely hold a party complete with homemade grog and sea chanties. I'm pretty sure, however, that the Japanese couldn't talk like a pirate if they tried. It's hard enough for them to speak English. The best I can do, therefore, is to get into the spirit of things and enjoy a piratey atmosphere at home.
To that end, I offer you my artwork of Skull from PvP as a pirate for your desktop. A small piece of it is at the top of this entry but a screen-size one can be downloaded here.
I also heartily recommend playing any incarnation of Monkey Island that you can get your hands on. This is a LucasArts adventure game for both PC and Mac that was inspired by the Pirates of the Carribbean attraction before the wildly popular movies came out. The flavor of the games is similar to that of the movies. In fact, there are some identical scenes in each (such as the dog with the prison cell key).
You can learn more about the games from two very good fan sites: The Legend of Monkey Island and World of Monkey Island. You'll have to search around a bit to find the games though, particularly the older ones. Aspyr ported Escape From Monkey Island to the Mac. PC users can get it from LucasArts. I'm not sure if the first few games, which were distributed on floppy, can be purchased anywhere anymore but there may be, ahem, some way of getting them for resourceful types. I replayed MI 1 and MI 2 over the last 4 days and they're still fun. I started MI 3 last night and plan on soldiering on to MI 4.
One of the most obvious ways to get in the spirit of things is to watch pirate movies. While the Johnny Depp movies are fine, for a real old salty dog experience, you have to turn to Robert Newton's hammy performances as Long John Silver. You can go with Treasure Island but for a full dose, his 1955 Adventures of Long John Silver television series which is available as part of a large and cheap collection of pirate movies is definitely the bee's knees.
At the very least, on September 19, try to wear a puffy shirt. ;-)