I'd like to point out my blog's wonderful companion map, which will give you several good ideas along that path through Alabama and Georgia: http://www.communitywalk....ie_lets_eat/map/939046
Dreamland in Tuscaloosa is a popular classic. Marie's BBQ in Heflin was pretty good - phone them first - and Turn-Around BBQ in Tallapoosa has some amazing Brunswick stew, one of my three or four favorites. I think that they close disagreeably early, though, about 2 pm.
Hudson's Hickory House in Douglasville is, sez me, a must-stop just for their incredibly interesting and curious barbecue "juice," as regulars call it. Very, very few other places have it, and those that do are copying Hudson.
If you're taking I-85 from Atlanta, I can also recommend The Smoking Pig in Pendleton SC, which hasn't made it onto the map yet. I thought that was very good.