Falling Water is definitely cool, worth seeing once in your life. That dude had one hell of an imagination! I did it in a day trip, so I can't help with the camping recommendations out there, though.
If you're looking to camp in eastern PA, well...where to start? Otter Lake is nice from what I've heard (haven't been there yet,) Blue Mountain looks nice (ditto--my trip there got squashed back in October,) and if you're up near the PA Grand Canyon/Wellsboro area (central PA,) both Petticote Junction (on Pine Creek) and Canyon Country are nice (stayed at both last year.)
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)25
2014 Harley Davidson FLHX (XLR cargo)
2014 VW Jetta TDI (diesel sipper, camping support vehicle)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)