From parades, to the 'wearing of the green' , to making "green" crafts, food and fun - people love St. Patrick's day. Some places going as far as dying rivers green, to mark the holiday of Ireland's patron saint.
The biggest observance of all is, of course, in Ireland. Almost all businesses, with the exception of restaurants and pubs, close. Being a religious holiday as well, many attend mass, where it is the traditional day for offering prayers for missionaries throughout the world.