Picking just one or two is too hard! Pennsylvania is our home state so I'd recommend Gettysburg, historic sites in Philadelphia, Harley factory tour in York and Steamtown National Historic Site in Scranton.
I have a split personality - I like to plan but I don't like to stick to a rigid schedule so I made Google maps with links to all of the places where we might want to stop. Link -
https://maps.google.com/maps/ms?msid=210711839070103512786.0004ee90b7077185f193f&msa=0&ll=54.367759,-105.292969&spn=64.493796,128.496094 Everyday I open the correct map and decide which direction to go and what we want to visit along the way.
Have a great trip!