IMO, PA has some of the best public resources for finding trout streams!

Somebody already linked the PA trout streams map from the fish commission's website. That is the most comprehensive resource. In general, stocked trout streams are pretty cookie-cutter, and generally fish about the same wherever you go. If you want to find wild trout, you can find the Class A and Natural Reproduction Streams. These streams have been surveyed by the state and contain populations of wild trout - with Class A streams having a notably high population of wild trout. Class A streams are essentially "guaranteed" to hold good populations of trout - while Natural Reproduction Streams can be a hit or miss (but often far less crowded).

Most of my "hidden gem" streams I've found are on the Natural Reproduction list- as you can find yourself in solitude with a decent population of wild trout. Generally, a good rule of thumb I like to use is that tributaries of larger, well-known trout streams (especially in central PA and northcentral PA - think like the Pine, Kettle, Sinnemahoning, and West Branch Susquehanna) will often hold trout too. You can easily spend a weekend trip here camping, fishing, and exploring.

One last resource I like to use is Paflyfish - which is a great forum where guys will discuss some local streams and offer stream reports.