I third the ferry suggestion combining your NY and jersey into a single three day block. Arriving in Philly, catch SETPA to center city. From Philly, catch either bolt (nicest) or megabus to NY unless you have the extra dough for the train (which saves an hour) but starts at $34 (booked in advance). on teh return, take Amtrak to baltimore...if you wish, you can book a layover, an afternoon, in wilmington and walk around downtown wilmington to see the sites, such as they are. I'd tack the extra night saved onto your philly itinerary since it's cheaper than NY. catch train from wilmington to baltimore. that said, there is one other option. catch the cheaper SEPTA train to wilmington during a 3 day stint in Philly (about 50 min each way) and then book a direct Amtrak ticket to baltimore from NY.

One other suggestion for an easy visit to New Jersey. Camden, NJ is right across the river from Philadelphia, and there are two waterfront based attractions there, the Adventure Aquarium and the battleship New Jersey. An especially good way to go there in summer is to take the ferry that runs to Camden across the river from the Independence Seaport Museum.

Given how scuzzy and unattractive Camden is (arguably worse than Trenton, if that's possible), I would strongly recommend limiting your Camden experience to these attractions in broad daylight only.

Y'all ROCK! thank you so so much for all the help and suggestions. Our first thought of plans have changed a bit and we are more flexible with how long we are staying in any one place. I will be sharing this with my friends so our trip can be awesome with/because of your help.
Stacey

I have to disagree with the others that there isn't a reason to visit Atlantic City. I like Atlantic City and I'm not a gambler. It is very easy and convenient to get there on NJ transit but they are right that there may be more convenient places in NJ to stop.