Directions: Park runs from the Delaware River to Pine road, through Northeast Philly. Best access is from the corner of Algon & Bustleton Avenues. Entrance is from the north side of Algon. As you go down the path into the park, take the horse trail to the left. there are miles and miles of trails- different terrains, etc. There's a bike path, but it's paved. You want the horse trails. Just start running and you'll find many challenging paths.
Miscellaneous Information: There's an organization called the Friends of Pennypack, who publish a decent map, but it's more fun to just put one foot in front of the other.