Baltimore's Inner Harbor is good for a few hours. DC is great for at least a day, could easily get 2 or 3 days out of DC. Charleston, SC is really nice. It's RV friendly, but it is a good 45 minutes off I-95. Savannah isn't RV friendly. There is some good history to see (Fort Pulaski and Old Fort Jackson to name a couple), but not much else. River Street is nice if you like shopping and there are a few nice restaurants.
Jekyll Island in GA is good for a few hours. If you are bringing bikes, there are lots of bike trails throughout the island. It's about 20 minutes off I-95. You do have to pay to get on the island - $6 for a car, $10 for RV.
St. Augustine in FL is really nice. Get on A1A and hit the beach. Historic Downtown St. Augustine is really nice and there is a free RV/Bus parking lot a few block walk to the historic section.
There's a lot of other great stops in FL, but you didn't say where in FL you are headed.
-Michael
Michael Girardo
2017 Jayco Jayflight Bungalow 40BHQS Destination Trailer
2009 Jayco Greyhawk 31FS Class C Motorhome (previously owned)
2006 Rockwood Roo 233 Hybrid Travel Trailer (previously owned)
1995 Jayco Eagle 12KB pop-up (previously owned)