Old Dominion Beer Festival! 
I was just cruising through craigslist and I saw that they had an event calendar. I'm sure they've had this for some time now, but I'd never noticed it before. So I decided to check it out and stumbled across something pretty interesting for this weekend: The Old Dominion Beer Festival! Tickets are $12, it's about 40mins from DC at the Old Dominion Brewery and it looks pretty cool. It runs until 11pm Friday and Saturday and until 7pm on Sunday. Once you buy your way in, 6 oz. beers are $1 a piece, which seems like a pretty good deal. 10 6 oz beers + entry = $22 for 60 oz. of all sorts of beer. For example, some of the breweries planning on attending are:

Chimay Brewing, Dogfish Head, Allagash Brewing, Magic Hat Brewing, Tuppers'Brewing Co., Fordham Brewing, Abita Brewing Co., Sierra Nevada Brewing, Hofbrau Brewing, and Flying Dog Brewing

There are many more, but those are the ones I'd go for. Plus, there's live music, food, games, and crafts. Looks pretty schweet to me.