Not only is the WPIAL amazingly competitive, but District IV or the "Coal Region" is too. Here we have:
-Bloomsburg (not really dominant but we've been good over the past few years)
-Southern Columbia (PIAA titles in 94,02,03,04,05,06 and have won the district 17 of the last 18 years...since '94 they've been in the state title game 12 times)
-Mount Carmel (one of the winningest teams in the country, 3 titles in 98,00,02)
-Berwick (had Ron Powlus play for them in '92, were considered national champions by USA Today a few times, several state titles)
I really shouldn't group us in with the last 3, but there's a TON of state titles all within a 30 minute drive of each other.
I'd also add the Philly region and Lehigh Valley as huge football places. Philly has the PCL, then teams like CB West, Ridley, and Lansdale Catholic in the suburbs, and the Lehigh Valley is nuts too. Liberty won the AAAA title last year out of there, and Parkland is always a force.