I’d especially appreciate off-the-wall answers. I’ll be there the last weekend in July.
I’m a nerd; I love pop art, Americana, comic strips, science…
What’s the thing a nerd *has *to do in Atlanta?
This may sound silly, but I love to visit the Coke Museum. It has history and fun facts and a Coke bottle based kinetic sculpture. My favorites are the soda fountain where you can sample Coke products from around the world (don’t miss the Italian Soda) and a little theater in which you can watch Coke commercials through the decades.
I still get a little verklempt during the “Teach the World to Sing” commercial. :o
ETA: Hit the aquarium while you’re in the neighborhood. It’s nice.
Little Five Points. It has just about everything you’re looking for. (Probably not the science.)
We also have the Stone Mountain Laser Show. Huge stone mountain with Civil War, um, heroes carved into it, onto which they project a laser show nightly. It’s quite a bit outside Atlanta though.
And there’s the Georgia Aquarium.
Tell us more about you, and us Atlanta dopers can make some suggestions. How much time do you have? How much freedom to travel to nearby suburbs?
You mentioned nerdy stuff. There’s always Fernbank. http://fernbank.edu/
If you like sports, the Phillies are in town against the Braves.
One local website for the happenings around Atlanta is http://www.accessatlanta.com/
Another website that’s appropriate for most dopers the Creative Loafing website at http://clatl.com/
I’m pretty sure you can search both sites by date.
I’m actually in town to see two baseball games (Nationals at Atlanta), and I love all kinds of kitschy things and science-y things and nerdy things and stuff.
Does anybody have an in to the Cartoon Network so I can get a tour? 
There’s a store that sells Cartoon Network and other WB stuff in CNN center. In my opinion it’s not worth going out of your way for, but if you’re already at CNN Center it’s worth walking through.
One good thing is that World of Coke, the Aquarium, CNN Center, are all in easy walking distance of each other, surrounding Centennial Olympic Park.
Since you mentioned both cartoons and pop art, you might be interested in the High Museum of Art. They have a spongebob exhibit.
pop art and Americana: Another recommendation for the World of Coke. It’s a decent price, $14, for about two hours’ worth of unique museum in downtown Atlanta, and then at the end there’s a room where you can gorge on most of the global Coca-Cola soft drink products for free. There’s also a large gift shop if you’re one of those people who collects stuff with the logo on it.
nerd: There’s a Medieval Times near Atlanta. I’ve never been to one but my impression is you get a huge dinner and a live show of knights and whatever it is that they do.
nerd and a certain value of “Americana”: Stone Mountain
science: Georgia Aquarium, which is 100 yards across an open park from the World of Coke.
One more tip, if you’re bringing your car, you can park in surface lots on Marietta St for $5, much better than the $10 or $15 garages one block over.
If you’re not driving and you like drinking, Sweetwater Brewery runs a great brewery tour where you also get a pint glass and 6 x ~half pint samples for $10.
I’d disagree with the Georgia Aquarium. There are much better aquariums out there, and the one here is very much focused on the entertainment side of things - definitely not science heavy. I only say go if you love aquariums (unless you have kids with you, in which case, it’ll occupy them for an afternoon.
Possibly the Cyclorama. Out in my part of town is the Waffle House Museum - I’ve not been there, so can’t speak to what it’s like - it does look like you’d need to call to set up a time to visit if you wanted to go there.
For a great dinner, try Houston’s. Excellent food and atmosphere!
Nerdy and a great way to see the city a little bit:
I live in the area and did this with another family and it was a great way to see bits of the city I don’t normally get to see. There is no time limit, the points don’t REALLY matter, and the mixture of clues and learning your way around gives you a great sample of downtown. It works out to be about three or four miles of walking plus a quick round trip on MARTA.
Oh, and while I’m not a big fan of zoos, I did go Monday, and if you like pandas, they aren’t going to be here much longer, might be worth a visit.