Not counting school trips as holidays, I'd have to say domestic plane trips to visit friends (as a houseguest in the parents' home) around Christmas of my freshman year at college. We went into NYC (using public transportation, mostly suburban buses from NJ but also the subway system) for NYE, the first and only time I saw the ball drop in person.
ADDED: The parents had a Playboy Club key and invited us to use it for drinks and dinner (alcohol was legal at 18 in NY then) there, among the bunnies, that evening. When I look back, I'm amazed that we were able to reserve a table for NYE; maybe the parents were more VIP than I had realized.