Society for Creative Anachronism (I'm still too drunk to spell, so I may have to edit that later). We dress up like morons in medieval duds (anything before the year 1700), then we pich our ...ähum...tents (well, they are whatever an army of whatever culture you are depicting would have lived in - ours in a Norse A-frame Oseberg replica, basically). Sometimes we have tourneys, but sometimes we have wars. In the tourney it's a one-on-one round robin thing, but in the war it's actual screaming hoards attacking eachother all in armour (the best you can afford or make, sometimes actual scale mail, chain mail or plate armour, sometimes old hockey equipment dressed up to look right). At the last event there were 1600 of us attacking with swords, bows, axes, maces, and even a trebouchet. Oh, and then there are the rapier dudes and dudettes, but they don't parttake in the battles with rapiers, obviously. Sometimes there is equestrian and dog races, too. It's loud, hot and stinky at war, but it is also awesome. Everyone looks out for everyone, but your parents will have to sign a waiver that it's OK for you to be there. Lots of people get drunk, but one really, really doesn't have to be pagan or do drugs or drink or whatever. Hell, we bring our kids, and they love it (yeah, they get to beat up on the ogre with bofferswords and stuff, too...that helps, especially if Dad's the ogre - I am going to make Uncle Johan be the ogre next time). Anyhow, you make it exactly what you want to make it. I can get you a website if you PM me.
T. (who edited while still intoxicated)