There are many, many trails in Pennsylvania. With a goal of hiking most of them, I am far from achieving such a goal. Even though you will find specific details about trails and hiking within Pennsylvania on this website, there are plenty of other websites that offer information on PA trails. If you plan on hiking any of these trails, I would highly recommend visiting it's website first as you can learn some valuable information.
Here is a short list of some of the other websites that offer information specific to a trail or group of trails. If you know of any other trail websites, please let us know. Some of the websites listed here are trails that I've hiked, while others I have not.
Pennsylvania Department of Conservation and Natural Resources - A good place to start when investigating hikes in Pennsylvania. Also has a lot of information on State Forests and State Parks as well.
Allegheny Front Trail - A relatively new edition to the hiking trails of Pennsylvania, this trail is situated in and around the Black Moshannon State Park.
Conestoga Trail - A hiking only trail that stretches 61 miles through Lancaster County in south-central Pennsylvania.
Quehanna Trail - The Quehanna Trail is a 75-mile loop trail in the Moshannon and Elk State Forests. The Trail passes through some of the most wild and beautiful country Pennsylvania has to offer.