I am a fan of Octoberfest.
It's a lovely fall outdoor festival, it involves lots of food, much of it served on sticks, and beer, and much of the beer in the form of seasonal limited releases. Plus, it's got historical associations, so the beer and junk ethnic food are educational exercises. What's not to like?
Octoberfest began in Munich, where it's still a huge celebration, attracting thousands of visitors every year. The first Octoberfest was part of the festivities around the marriage of Crown Prince Ludwig (later King Ludwig I) and Princess Therese of Saxe-Hildburghausen in October of 1810. There were several days of celebrations, including outdoor parties, parades and horse races. The city fathers of Munich have since increased the dates of the festival (it's just under three weeks) and moved it a bit earlier in the year; it starts in September, and ends the first week of October.
Now, all sorts of countries all over the world celebrate the turning of fall, harvest, and beer—places like Hong Kong, Vietnam, and even Palestine take part, as well as communities all over Germany and the U. S. There's a decent general discussion of the history, and modern permutations, of the Octoberfest on WikiPedia. The official Web site for the Munich Octorberfest is here; I note that they have their very own iPhone apps.
One of the best parts of the German celebrations in Munich and elsewhere is that brewers make a special dark beer called Maß, which is often only available for the weeks (or days, in some places) of the Octoberfest. Traditionally, Maß is served in large (often commemorative souvenir mugs) that hold a liter of beer. A maß is unit of measurement used for liquid, cognate with English mass. It's just over a liter in size. Every year beer fans, and economists both watch the price of Maß as an indicator of the current state of the economy, and a forecast of things to come. The price went up this year.
Fall Seasonal brews, like Octoberfest beers (traditionally a malty amber lager made in March, then barrel aged and tapped in the fall) or Harvest ales (traditionally a small batch beer brewed with high quality just harvested ingredients that might include special flavorings and hops, and a bit higher in ABV) and Pumpkin beers (made with real pumpkin and various spices for flavoring) for carefully, since they used to be hard to spot. Now, it's a lot easier to find seasonal brews because of sites like Seasonal Beer that let you search for seasonal brews, and the food to serve with them.

