I second Pennwood. If it is not on your way, it is still worth a detour. It is about 45 minutes east of I79 on I80. Cook's Forest is nearby and worth a look.
Oil City/Titusville has a couple of nice campgrounds.
If your heading north, you may want to check out the Kinzua Dam area, near the New York/Pennsylvania border. Lots of camping available there, but it is mostly without hookups. There is a KOA in the forest also, northeast of the dam site.
2003 GMC 2500HD 4X4 D/A Ext. Cab
Propane Powered Honda EU2000i
Lots of Hot Sauce!
Air # 283