You have lots of options. looking for a specific beer look here:
Looking for something close look here:
I would recommend Haymarket as a good brewpub and a short cab ride to greektown:
Or you can go to the Binny's South Loop location (a short cab ride or nice walk) It is a beer store but after 3:00pm they have a nice selection of taps in there little tap room and they can also chill any bottle in the store for you. 3Floyds Arctic Panzer Wolf was still on the shelves last night, as were many other good beers.