If you like art museums I would recommend Brandywine River Museum near Longwood Gardens for the Wyeth Family paintings. If you visit the area during the Winter and look at some of Andrew Wyeth's paintings of the Brandywine Valley then you will see how accurately he depicted the region. The Pennsylvania Academy of Fine Arts (PAFA) in Philadelphia is a gorgeous building with fine American Art. The Barnes Foundation in Philadelphia has a fine collection of Impressionist Art.

For hikes, the recommendations of the other Ziners are the best ones with my favorite being Ricketts Glen. I hiked mainly in Eastern PA with several excursion to North Central PA. I have not tried Western PA. For the Philadelphia Area I would add Tyler Arboretum, Bowman's Hill State Wildflower Preserve (if you are visiting Washington Crossing Historic Area) and the Pinnacle and Pulpit Rock near Hamburg (near Hawk Mountain). For Poconos Area, I would add Hawk Falls and Boulder Field at Hickory Run State Park, If you are visiting Bushkill Falls then drive a bit further North on route 209 to visit even more waterfalls at the Pocono Environmental Education Center, Dingmans Waterfalls area, George W. Childs Recreation area, Raymondskills Waterfall and another waterfall still a bit further north on route 209. A bicycle ride at Lehigh Gorge along the rails to trails path is nice especially when the rhododendron are in bloom. My recommendations vary a lot in degree of difficulty and time needed to complete. If you don't want to hike a lot then some of these areas can be visited with minimum effort.

Sincerely,

Ed Wickham I live a few miles from Philadelphia