Mount Davis is about an hour or two outside of Pittsburgh. Highest point in PA. Some pretty decent hiking, and it's also not far from some natural waterslides and the Youghiogheny (white water rafting, hiking, camping, etc).
I grew up in Lancaster county, which is full of both historical things to see and do as well as some things related to the Amish culture that is largely present there. I've since moved to Philadelphia, which is also full of historical things to see and do, plus both places have great food (in different ways). Either one is a nice trip, and that's only a tiny portion of the state! Northern Pennsylvania is full of places for hiking, off-roading, camping and things like that. Overall it's a great state to visit (and live!)
I would consider seeing the Pennsylvania Grand Canyon or going to see the Elk in Elk County. if your here in the late summer you should consider the Little league World series in Williamsport.
If you are a rail fan,consider the Horshoe Curve in Altoona or Steamtown in Scranton.
Pennsylvania is also home to many dirt track racing events from pure stocks to Supeer late models and sprints.
Chalk up another vote for Shady Maple. Just make sure you wear your stretchy pants!
I'd also say that Gettysburg is definitely worth a visit if you're in the area. As one of the bloodiest battles ever fought on American soil, it's really quite moving to see where our ancestors fought and died for this country.
Of course, Gettysburg is only one of many historical landmarks; if history is what interests you, PA is chock full of places to see!
EDIT: Almost forgot about State College! If you can get tickets to a Penn State game, definitely stop by. We've got the second-biggest stadium in the nation, and the greatest show in college football!
Two words for any Jeep owner: Rausch Creek
from their site:
"Rausch Creek Off Road Park is devoted to providing a fun legal place for 4x4 off road clubs and organizations to go "wheeling." The park consists of 1,700 acres of easy, intermediate, and hard trails. Rocks, bowls, hills, the glacial "Rock Creek", club friendly trails, and free on site camping combine to make Rausch Creek a unique 4x4 destination. We are not open to quads or bikes. For information about quad/bike riding, go to rauschcreekracing.com."
Well there are many places to visit and I will repeat what other people have said,
Shady Maple in lancaster, rausch creek, Gettysburg for the civil war re-enactments as well as the ghost hunting places. There is a lot to do in PA. You can also head to bethlehem to check out the Sands Casino, and over to the Allentown Brew works for very good food and lots of beer.