I asked some locals I ran into about jumps/trails a couple of months ago. They said all of the local trails have been plowed (I specifically asked about the Manville trails) and they said they go to PA when they get that itch.
There used to be some decent trails in Yardley, PA, but I haven't been by there in a number of years. Looking at Google-maps, I see some hints they are still there.
There was some off Rt 13 near Tullytown, PA, but last I drove by, it appears they were plowed (not that they were all that great to begin with). Google still shows them, but it looks like an old photo.
We can be jealous of my team mates down in DC. The builders there actually got their jump trails near I-495 sanctioned/approved by the park service that managess the land they're built on.
It is general rule-of-thumb to never post trail locations online. If you're lucky, somebody may PM you details.