Beer is an organism, and like any organism, it goes through stages of development. This may not be obvious to the average beer drinker who's used to finding beer in its adult state, in pint glasses or six-packs. There's conception (the mash), gestation (the boil), and development (fermentation). Eventually you get to a stage where you can feel the baby kicking, and get a pretty fair sense of what will happen in a few days: conditioning.
The first time I experienced beer pre-packaged, I was at Portland Brewing's then-new plant in NW Portland. (It's called MacTarnahan's now, though I keep hearing rumors they plan to return to the old name.) I had been writing for Willamette Week for about five minutes and was beginning my tour of the city's breweries. I don't recall who took me to the massive tanks outside the building, or what beer we sampled. I mainly recall thinking that it seemed a little transgressive to be opening a spigot on the side of the tank and slugging back raw beer. (I had a similar experience when in second grade I went on a field trip to a farm and milked a cow.)
That lovely experience is the inspiration behind Zwickelmania, the annual event organized by the Oregon Brewers Guild that turns participating breweries into open houses for a day--so everyone can cruise up to a tank for a wee zwickel.* That day is tomorrow, from 11am to 4pm.
Click on the poster for details about where the events will be happening--and take note of the descriptions provided by the breweries. Some breweries offer tours but not actual zwickels; others give you the full monty. My recommendation is, obviously, always, the full monty. Some breweries are releasing new beers, others are reprising old beers, others have specialty menus, and still others appear to be winging it. Plan accordingly.
Another cool thing: shuttles are available. Check the Brewers Guild website for times and locations (follow the same link).
*The German Beer Institute offers this definition: "The name Zwickelbier stems from the sampling cock ("Zwickel" in German, pn. tzvickle) mounted at the outside of a cask or tank to take tastes for assessing the brew's progress during fermentation." Whether the Brewers Guild's extended uses--as a verb to indicate the act of pouring beer from a tank and as a noun to indicate the beer thus poured--are traditional, I can't say. But it seems to have taken root.