If I may contradict Littleman, Williamson Bros. is nowhere close to as good as they used to be, and I’d strongly advise against a visit. It was the subject of a pretty lengthy thread here:
 
http://www.roadfood.com/Forums/tm.aspx?m=526260&high=williamson http://www.roadfood.com/F…60&high=williamson
 
There are many other very good BBQ places here in Cobb, including Wallace (my favorite), Thompson Bros. and Big Shanty Smokehouse.  I’ll agree that Rib Ranch is pretty good.  It’s actually the closest BBQ to my house and not a thing wrong with it, but I almost always drive a little further for better.
 
I haven’t stopped there in years, but there is a place in the Dallas/Hiram area called Briar Patch BBQ.  I remember being disappointed in the canned veggies, but the pork was good.  It seems to have avoided the blogger radar, but they have a website here:
# http://www.briarpatchrestaurant.com/
 
Another idea is Doug’s Place, which I tried for the first time Saturday and loved.  This is a quintessential side-of-the-road southern meat-n-three in Emerson, which is just your side of Cartersville off I-75 exit 283.  The building’s been there since 1890-odd, and even though most of the staff are much younger, they know how to fry up some fine food, from excellent chicken livers to green tomatoes.  All Roadfood regulars would love this place.

Marietta GA is 18 miles E of Dallas GA.  There’s good BBQ there at  Poe’s, Sam’s, Rib Ranch and Williamson’s.
 
Dave Poe’s BBQ @ 660 Whitlock Ave., Marietta, GA. 770 – 792 – 2272.
http://www.davepoes.com/ContactUs/tabid/79/Default.aspx http://www.davepoes.com/C…/tabid/79/Default.aspx
Sam’s BBQ @ 4944 Lower Roswell Rd., Marietta, GA. 770 – 977 – 3005.
http://www.lostmountainbbq.com http://www.lostmountainbbq.com/
The Rib Ranch @ 2063 Canton Rd., Marietta, GA. 770 – 425 – 6276.
http://www.theribranch.com http://www.theribranch.com/
Williamson Brothers @ 1425 Roswell Road, Marietta, GA 770 – 971 – 3201.  http://www.williamsonbros.com http://www.williamsonbros.com/

Definitely Gumbeaux!!!!!  It’s right down Hwy 92.  Don’t miss it.  Hudson’s in Douglasville for BBQ too.  The Irish Pub is excellent too.  All on Bankhead right over the railroad tracks off 92.[8D]

Jim ‘N Nick’s Bar-B-Q is a small chain which has garnered much better reviews than most chains.  They have a location in Hiram.
 
The best Cajun cuisine in metro Atlanta is available at Gumbeaux’s in downtown Douglasville.
 
Beyond those two suggestions, I would suggest looking east to Cobb County – where numerous options await.

 
Another idea is Doug’s Place, which I tried for the first time Saturday and loved.  This is a quintessential side-of-the-road southern meat-n-three in Emerson, which is just your side of Cartersville off I-75 exit 283.  The building’s been there since 1890-odd, and even though most of the staff are much younger, they know how to fry up some fine food, from excellent chicken livers to green tomatoes.  All Roadfood regulars would love this place.

  Doug’s Place – which a friend of my calls the Emerson Hooter’s – is a great choice for a traditional southern meat and vegetable meal.  There can be a lengthy wait for a table during peak times, which says quite a bit about the food quality.