We are driving from Philadelphia to Orlando in the second week in September. What is worth seeing on the way, i.e. it is our first time in the U.S. and we need any guidance we can get on the "must see" spots on the route

The only worthwhile stop that comes to mind is Washington DC. Other than that, it's a pretty long and boring 950 miles or so.

We did that drive in 1998 and 1998, spent a night in Savannah one time and a night in Charleston the other and enjoyed ourselves. I recommend stopping somewhere south of Virginia so you can get past all the DC area traffic the first day (the DC traffic is hugely annoying). South of Jacksonville, we picked up Route 17 and took that down to route 19 through the Ocala Forest (the road is not used that much and is more scenic than the interstate), then went through Mount Dora, an interesting little town. On the way back we stopped in Charlotte, NC.
BTilke

David
Depending on how much time you be over here, I would agree with Celeste. If you are only going to be here for a week, stop in Washington to see the mall museums, monuments, etc., and then head straight to Orlando. While there are some nice places along the way, I would condsider none of them a "must see".

My suggestion would be to skip taking 95 through Baltimore and Washington DC and instead take Route1/13 through Delaware, Maryland and Virginia - and then take the Chesapeake Bay Bridge Tunnel back over to 95. A lot less congested and rather quaint road. Perhaps a bit longer than 95 - but more scenic for your first part of the trip.

Thanks to all for your replies. Erika, your suggestion has made me consider the Shenandoah Valley area. I'm sure it is well worth a visit.

May I re-phrase my original question? If there are no "must see" places along our route, what are the most interesting/least monotonous roads to travel?

I am not sure why my suggestion made you consider the Shenendoah Valley - since they are in two completely opposite directions (DE, MD and VA are east of I 95 and the Shenandoah Valley is well west). The Chesapeake Bay Bridge Tunnel is really cool (IMHO) and if you are looking for neat places to stop - then Chincoteague Island would not be too far out of your way on this route.

I have made the Philly - Florida trip countless times in my life (grew up in Philly with g-parents in Florida) and I-95 is all the same state after state after state. Are you looking to seriously extend your travel time from Philly to Orlando (in which case full day stops in Baltimore and Annapolis MD, Washington DC, Williamsburg VA, Savannah GA and St Augustine FL would all be worthwhile). However - if you are looking for simply scenic routes then I would say it depends on what kind of scenery interests you.