I've seen several @ Moraine State Park while fishing Lake Arthur. I was there last Saturday while fishing the North End of the lake and one flew over. Similarly, observed one perched in a tree last year around Nealy's point.
Not sure this qualifies as 'hot spot', but certainly their are Eagles around the Lake.
I spend a good deal of time around the Shenango Lake area in Mercer county. I have seen a good deal of Bald eagles and eagle nests. The Rangers are very insightful and are willing to share their sightings and offer advice on where and when to be watching. Alot of Osprey's out there too. what a huge bird that is! Best of luck!
Hemlock Road from Warren up to the Kinzua dam, especially in the winter. Two winters in a row on the Christmas bird count I've had 5 different eagles within view at the same time. More than once I've seen two in the same tree along that strectch of river. Drive slow, park at pull offs and watch.
Winter is best because the lake is frozen, so more eagles are on the river.