St. Joseph's Day is a big Feast for Italians because in the Middle Ages, God, through St. Joseph's intercessions, saved the Sicilians from a very serious drought. So in his honor, the custom is for all to wear red, in the same way that green is worn on St. Patrick's Day.
After Mass (at least in parishes with large Italian populations), a big altar is laden with food contributed by everyone. Different Italian regions celebrate this day differently, but all involve special meatless foods: minestrone, pasta with breadcrumbs (the breadcrumbs symbolize the sawdust that would have covered St. Joseph's floor), seafood, and, always, fava beans, which are considered "lucky" because during the drought, the fava thrived while other crops failed (recipes below).
The table -- which is always blessed by a priest -- will be in three tiers, symbolizing the Most Holy Trinity. The top tier will hold a statue of St. Joseph surrounded by flowers and greenery. The other tiers might hold, in addition to the food: flowers (especially lilies); candles; figurines and symbolic breads and pastries shaped like a monstrance, chalices, fishes, doves, baskets, St. Joseph's staff, lilies, the Sacred and Immaculate Hearts, carpentry tools, etc.; 12 fishes symbolizing the 12 Apostles; wine symbolizing the miracle at Cana; pineapple symbolizing hospitality; lemons for "luck"; bread and wine (symbolizing the Last Supper); and pictures of the dead. There will also be a basket in which the faithful place prayer petitions.
The cry "Viva la tavola di San Giuse!" begins the feasting and is heard throughout the day. When the eating is done, the St. Joseph's altar is smashed, and then three children dressed as the Holy Family will knock on three doors, asking for shelter. They will be refused at the first two, and welcomed at the third, in memory of the Holy Family's seeking of hospitality just before Christ was born. This re-enactment is called "Tupa Tupa," meaning "Knock Knock."
I think I'm going to wear some red tomorrow. Probably not all red, but some. =D Interesting stuff no doubt!