where are you staying and when will you be there? chomp and stomp is a local neighborhood chili/blues festival which is a lot of fun. i went last year and had a blast. get there early, though. parking is a pain and the chili goes fast.
sweet auburn curb market will give you a great taste of local food.
typical touristy things like the aquarium, cnn center, stone mountain.
a lot of good restaurants and nightlife in midtown and buckhead.