There are many interesting places in PA and NJ. These are some of my recommendations:
Philadelphia - history, museums, food, and architecture
Bethlehem - history, architecture (there is also a casino if you like that)
the Delaware River (south - between Easton and Philadelphia on both sides of the River) - unique architecture, small villages and river towns, art, food, geological sites mentioned above (north)- the Delaware water gap - Wayne county is beautiful and rural
NE PA and anthracite region - (Scranton area) not the most beautiful countryside (stip mining etc) but interesting historically (mining, Molly Maguires etc) and culturally (customs from Eastern Europe, good pizza, and a unique brogue, heyna) - also Jim Thorpe is very nice (architecture, hiking, trains, art)
Central PA - this area is not well travelled but very nice. It is very rural (mostly farming valleys with tree covered flat ridges) mostly a farming area with many Amish and Mennonite groups (sometimes the majority). There is not much sprawl. Belefonte is nice, as well as Lewisburg and State College. This area doesn't have many sites but it is interesting as awhole.

I am not as familiar with western PA.