Here's a map of some of my favorite breweries located around Philadelphia.
For those of you serious about your beer, beer drinkers, snobs, and conousiers (spelling?), you must go to Victory Brewhouse. Triple Golden Monkey Beer is the highest alcohol content beer there, at, if I remeber correctly, 9.5 - so don't go crazy on it. And all brews there are fresh, with seasonal and even weekly brews. The food and entertainment has gotten steadily better over the years as well. But I wouldn't recomended for a date on a friday night, its usually packed and sometimes standing room only. It is more laid back during the week, and is not to off the hook with pricing. If in the West Chester Area, I recomend stoping by Victory.
I recommend the Iron Hill Brewery - the food is fresh and awesome, and so is the beer, that flows out of hugew underground chambers, that are connected to huge vats behind the bar - The underground chamber keeps the beer just above freezing, so its nice and cold when it hits your lips...
Oh and I agree with tom - Victory Brewhouse in Downingtown has great seasonal and staple brews - the food isnt as good as Iron Hill - but there beer is def superior...Cheers.