|Definitely check out Tybee Island if you get a chance like Odyssey said. If you want to just stay in the city, there is plenty to do in the historic district. Places to see are River Street, which is all old cobblestone roads and there are tons of shops and great places to eat along there(Tubby's Tankhouse has some of the best shrimp i've ever had). Then you'll want to check out Broughton Street, Bay Street and City Market. There are two old time theaters off of Broughton St. that often have shows, movies, plays, or comedians there.
There is a museum in town, The Telfair Museum of Art, which has a brand new huge building off of Liberty St. I think. Also, there is the roundhouse museum which is a train museum which is pretty cool. There are a lot of art galleries in town and many buildings own by my college the Savannah College of Art and Design. You should try to check out Bergan Hall, the photo building if you can find somebody to take you in there. That's located on MLK Blvd. Also, check out Forsyth Park, usually tons of people there on weekends and nice days.
I'd recommend staying downtown in the historic district. If you go south side it becomes very commercialized, just malls and strip malls pretty much. I hope the weather isn't too hot when you go there. Good luck!