I have been twice, but both times we stayed outside of downtown because it was really expensive (we are broke college kids). But I know there is a B&B that is supposed to be awesome. If I remember the name, i will post it. Also i would stay near riverfront/riverstreet? I think there is a hilton or a hyatt and a hampton inn. I can't remember. I am so bad at giving travel advice. But check out Virtualtourist.com.
i love savannah! i have been there twice, but the first time i stayed with a friend, and the second was while we were staying at hilton head. actually, hh is only about 45 minutes from savannah, and if you love the beach maybe you can take an extra day or two and stay there?
if you are into antiquing, the riverfront area has a lot of neat shops. i've heard lady & son's restaurant (paula deen's restaurant) is really good, but i have not eaten there. if you like southern food, i really recommend mrs. wilkes' boardinghouse. it's cheap, and served family style in a cafeteria like setting, but oh.my.god. the food was amazing. not the healthiest meal ever, but the best fried chicken i've ever had (and collard greens..blackeyed peas, biscuits..!)
SCAD has a really cute shop downtown, too. it's all stuff made by the students (artwork, crafts, etc) and the stuff is pretty neat.
i've been a few times, but only stayed in a hotel once. we stayed at the days inn -- it was not too expensive (not luxurious but fine -- a typical days inn) and you could walk to everything.
if you're going to have a car, there is a great seafood place on tybee island (probably a 10-15 minute drive). it's called the crab shack, and it's one of those places that's really casual with just picnic tables , and you can get a low country boil (yummy mixture of clams, mussels, shrimp, sausage, corn, and potatoes), great oysters, and pretty much whatever other kind of seafood you want. not super expensive, great seafood.
riverstreet inn is great. old hotel sort of b&b style but its big and right on river street.
the mansion on forsyth park is new and i haven't stayed there yet but my boss stays there every time he goes to savannah. looks really nice when i make his reservations.
the kehoe house is a good b&b.
there is another famous b&b that i can't remember the name of. i'll edit when i think of it.