On the continent of Europe, across the pond from the USA, several countries celebrate Walpurgis Night, under a number of different names:

http://en.wikipedia.org/wiki/Walpurgis_Night

That Wikipedia article says this about the city of Uppsala:

In Uppsala, since the mid-1970s, students also go rafting on Fyrisån through the centre of town with home-made, in fact quite easily wreckable, and often humorously decorated rafts. Several nations also hold "Champagne Races", where students go to drink and spray champagne or somewhat more modestly priced sparkling wine on each other. The walls and floors of the old nation buildings are covered in plastic for this occasion, as the champagne is poured around recklessly and sometimes spilled enough to wade in. Spraying champagne is, however, a fairly recent addition to the Champagne Race. The name derives from the students running down the downhill slope from the Carolina Rediviva library, toward the Student Nations, to drink champagne.
A profoundly cultural festival, consisting of running down a hill, rafting on the river, then getting paralytic all night. I'm too old for this and will be staying at home. A waste of champagne in my opinion.