Irish soda bread!!!!! That's what we're having for our menu on St. Pat's day. Irish soda bread, cornbeef, cabbage and potatoes.
I've been around 'real traditional Irish' people for several years durring St. P day in the past and depending on HOW into it the party thrower and attendees are, you may want to do an Irish traditional food/beverage. I, myself, am not totally crazy into St. P day, but there are some that are and if the food isn't authentic and Irish, they'd be dissapointed! I brought shamrock cookies once and one person told me "Just cause it's green, it don't make it Irish! (we live VERY CLOSE to a town that has a large % of authentic, real, totally traditional Irish...and my BIL's wife is Irish- her parents are ticked if someone brings something that is not traditional!!! Not that everyone is like that, but some are!!!)" So, after that I learned my quick soda bread and butter spread recipe! That is my 'go to' Irish traditional food if I need to bring it somewhere.
Guiness is also good, but expensive...Irish cream liqour of any type would be good over ice cream (as a previous person posted). Irish coffee (coffee and good whiskey with a little cream on top) is good.