Of course everyone knows about the St. Patrick's Day Parade and if you can't be here you can watch it on their web site: http://nyc-st-patrick-day-parade.org. I remember YEARS ago, when it was a drunken free-for-all. Ah, those were the days. ;-) Now, if you're caught with an open container you're toast! (Or, Irish Sodabread toasted?) But what else is there to do? Obviously most of the events revolve around drinking. Duh! So grab and Guinness and go!
Ah, St. Dymphna, the patron saint of those with mental illness. You can start off with a visit to St. Dymphna, a pub in the East Village with a grand Irish Breakfast (Sausage, black pudding, eggs)! http://st.dymphnas.com/
From 1 pm to 11 pm at the Bohemian Hall and Beer Garden in Queens it's $15 bucks for unlimited green beer. http://www.bohemianhall.com/
At Loreley (which is actually a German place) it's officially an "Alcoholiday" and $35 from 9pm to 4 pm for unlimited beer and whisky. Don't know if it's green or not.
Union Square Wines is having a free tasting of Irish whiskies like Bushmill's, Redbreast and Jameson's as well as cream liqueur makers Coole Swan and Ryan's Irish. http://www.unionsquarewines.com/events