The Brooklyn Brewery is worth doing, if you'll travel a bit. Weekends are best, between 12 and 6. Get the East River Ferry from Manhattan to Williamsburg... Takes 15 mins over the river and then it's 5-6 blocks or so. To be honest it is easier to get to from Manhattan than a lot of other places.
In the brewery the tours are on the hour and the beers are $5 for 1 or $20 for 5 (you buy tokens).
When I was there last (this weekend) they had, on tap: pilsner, lager, east India pale ale, Weisse, anniversary, Hotter, Radius, Brown ale, Sorachi Ace and I forget what else. The cask was Brown Ale. Big bottles were $10 a go.
You can order pizza in.
In the surrounding area you have some of the best food in any of the burroughs right now, and you'll find great beer in almost every pub. An upside to the hipster / foodie intersection going on.