Depending upon when you choose to visit, you might want to locate yourself on one of the Charleston area beaches in a house, condo or villa for the week (weekly rentals only during the summer months) and then do a day trip to Savannah.
There is tons more to see and do in the Charleston area, please read the Top Questions in the upper right and you will see. Also, for the most flexibility in your plan, you should rent a car for the entire week.
Something to think about.
Type your exact same question in the above search box, it will pull up many suggestions on this very topic, as it is a popular question.
If I were going to do 2 days in Savannah, I'd do them together instead of making a 4 hour+, round-trip drive twice.
Thank you all for your suggestions, and am researching other posts as suggested by Kiawahbeth. Lots to think about, and I'm excited about seeing both cities!
We went to Charleston last April and absolutely loved it. It is a beautiful, clean city and you won't be disappointed. We stayed at the Fulton Lane Inn, which was indeed lovely. A bed and breakfast in a great location. Walking distance to the daughters of the confederacy building, where they have an open market on some days. We did a horse-drawn carriage tour, which was charming. We also went to the Magnolia Plantation, which is spectacular. We rented a car and drove to Savannah. Have to be honest, Savannah is very pretty, a delightful little town, but one day there is enough. If you get a chance to read 'Midnight in the Garden of Good and Evil' before you go to Sav, you will enjoy it all the more.
So much history and culture in Charleston. Have to say it is one of the nicest cities I have ever seen and I would go back in a heartbeat. Enjoy
Charleston deserves the most time of the three. Savannah as mentioned can be seen in a day, though I would give yourself a day and a half. Beaufort could be done in a day trip, but many who visit it often wish they would stay a night as well. Be sure to check out the Old Sheldon Church Ruins along the way and if you have time, Hunting Island State Park.Edited: 24 January 2012, 02:25
Wow.......all of you have been wonderful with suggestions! Much appreciated!
Since you have 7 days to visit and you live on the West Coast do try to see both cities. You'll be able to get a good taste of both with the recommended 3 nites Charleston and 2 in Savannah. We spent a long weekend in Savannah last Spring and loved it. Be sure to stay in a B & B in both cities to help get a taste of the culture and atmosphere of the cities. Do walking tours, ghost tours, try some special restaurants that reflect the Southern influences and be sure to take lots of time to just walk the towns. You'll find enough to do to keep you busy and make you want to come back for more!