The Porter in Little 5 Points and The Brick Store in Decatur are must visit! Both always among the top 5-10 beer bars in America.
As far as breweries, Sweetwater and Red Brick Are the big two in the city. I would recommend Red Brick, not as crowded and more likey to see the head brewer and he is usally more than happy to talk shop.
I Decatur there is Blue Tarp and 3 Taverns which are both. Blue Tarp makes some sours. 3 Taverns is having their grand opening for their tasting room on Oct 11 and 12 and seeking tickets online. They are a Belgian style brewery with a head brewer from Belgium.
There are many other breweries in the area too and I know others will fill you in on them.