Charleston
Savannah
Fl pan handle.
Really comes down to time spent on road to get to your destination for the weekend. I love all three and have worked, vacationed in all three locations over the years. Not sure where in Ga you will be staying (assuming metro ATL counties) but all three are drivable. If you haven't seen a coastal city and you would like to see one, closer then Savannah.
Oxcoug is spot on about Savannah and the tour around the city is pretty cool. Take the time and walk around, taking in the humid south and locale. Not a bad choice and a quick, good getaway weekend.
Come back again, stay longer then hit Charleston and FL....so many options in the southeast.
Happy vacationing.