Over the years May Day has had many types of celebrations in many countries, from electing a May Queen to dancing around the traditional Maypole, with dancers circling the pole with ribbons. Since the original pagan holiday was a celebration of spring however, most of the celebrations involved fertility rites. (Woo hoo!)
In more recent history, May Day has become known as "International Workers Day" in commemoration of the Haymarket Massacre of Chicago in 1886, when Chicago police fired on striking workers seeking an eight hour work day. Demonstrations were called for in 1890 and were so successful that the event was made an annual celebration, which somehow became subsequent riots in 1894 and 1919.
By 1904 however, Labor Unions and the International Socialist Conference had called on all good Social Democrats to demonstrate enthusiastically in celebration of workers on May 1st. In 2006, migrant farm workers celebrated May Day with "The Great American Boycott", a general strike of all migrant farm workers in protest against immigration reform legislation. In 2007, a repeat of this protest ended in violence with an assault by officers of the LAPD. In 2008, the International Longshore and Warehouse Union celebrated by moving no cargo in West Coast ports as a protest against the Iraq war.
So before it becomes a more widespread part of the Democratic Socialism that seems to be becoming a greater part of our present and our future, let me be the first to wish for you (a bit sadly, I must add):
Happy May Day