How long do you want to stay/tarry along the way.
Charleston would be a must. Just north of Charleston, as you head up Route 17 there is the SeeWee to stop for lunch. Then there is Georgetown--has a LOVELY historic district and waterfront dating from Revolutionary War times. There are also some "minor" plantations just south of Georgetown.
Then the Pawley's Island/Litchfield/Murrell's Inlet area for the BEST seafood restaurants on the coast outside of Charleston, and some equal. At Litchfield is Brookgreen Gardens, a beautiful art and garden area on an old plantation. It was the home of the Huntintons, and Anna Huntington was a metal sculpress of great skill. The art collection and its display is VERY special. Their gift shop is nice.
Great shopping at the Hammock Shops in pawley's. The beach at Litchfield is beautiful, and the Litchfield Inn is ON the beach, and would be a good stop.
From Murrell's north is MB, and in my opinion, just keep going to Wilmington, about an hour and a half from Litchfield.
There is a major Tanger Outlet in North MB.

I also like Hunting Island State Park near Beaufort. When is your trip?

Southport, NC is also a great place to stop. It is off of 17 (the highway that you will take from Savannah to Wilmington; this also runs through Charleston) on route 133. It's a short deviation from the main highway and well worth the trip. It's a quaint little seaside town where a lot of movies are filmed. The downtown area is full of shops and restaurants with plenty of rocking chairs and tree swings available to sit and watch the waves.

I agree with both Hunting Island and Beaufort itself as a possible stopover point.

Midway between Savannah and Charleston is Old Sheldon Church. Burned by the British during the Revolution, rebuilt and burned by Union Troops. The columns and portions of the walls are still standing. At least once a year, services are held on the premises. Buried on the premises are important figures in SC and GA history. It's a few miles off the highway on a county maintained road in a beautiful low country setting. It's worth spending thirty minutes or more and helps break up the 2 hour trip from Savannah to Charleston.

Thanks everyone for the help. These posts are all helpful. Cant wait for out trip.