Plenty of them available, so it depends on what you are looking for in terms of amenities, price, etc. We've stayed at Skidaway Island State Park and the Red Gate campground. Skidaway is heavily treed with large sites and a pleasant "campy" atmosphere. Red Gate is an open grassy area (for satellite tv) and closer to the downtown attractions (riverfront, etc).
Consider also Savannah Oaks and the KOA. We haven't stayed at either, but reports seem good.