Something fun? That she's probably never done before?

The Aquarium
Andretti's speed lab
Movie @ the IMAX
Dinner somewhere in buckhead(Rusans is cheap/good/fun)
Some kind of sporting event tends to be fun if it can keep her attention
ESPN ZONE
FOX sports Bar and Grill
The Atlanta Zoo
Putput
Bowling

I mean there are a ton of things to do it really just depends on your wallet and what kinda girl she is.

My girlfriend and I are going to Rusans sushi bar tonight and then hitting up Andretti's afterwards just b/c we both like sushi, we both like going fast/cars etc and were both competitive....just some food for thought