Today is one of my favorite holidays on principle. I never do anything for it outside of having a doughnut because I am lame but the idea of today is very appealing to me.
For those who just woke up from a coma and are wondering what day and year it is, today is Mardi Gras, or Fat Tuesday, or Shrove Tuesday, or Carnival depending on who you are and where you live (and 2009 in answer to your second question).
Basically, it's the day before Ash Wednesday, which is the day when all of your Catholic friends are supposed to go have ashes smudged onto their foreheads.
Back in the day the Catholic Church decided that in order to properly celebrate Easter, all of the Catholic church goers needed to spend 40 days fasting, praying, reflecting on their sinful nature and to forgo having fun of any type whatsoever. And of course because Jesus was a fisherman (and to promote the fishing industry in general) no meat.
Naturally this pissed a lot of people off - particularly in Medieval Italy - because it sounded like a shitty way to spend 40 days so the Church compromised by giving everyone the day immediately before to eat, drink, throw beads, flash people, basically get everything out of their system and also to eat as much meat as they like (Carnival is a bastardization of the Latin 'Carne vale' meaning "eat as much meat as you can before it goes away for 40 days").
And, just like St. Patrick's day, you don't even need to be Catholic to enjoy it.
So go ahead and let off some February steam my friends!