OJ:
The problem is that IAD is kinda remote, out in the Virginia countryside. You might consider using public transportation to get a bit closer to the meet site:
Bus #5A( $3US ) leaves Dulles Airport at 40 past each hour on Friday afternoon and goes in towards the District, and terminates at L'Enfant Plaza where you can connect to the Washington Metro <
http://www.wmata.com>. From there you should be able to get to Union Station, and take an Amtrak or Metroliner train <
http://tickets.amtrak.com/itd/amtrak> in about 90 minutes to 30th St Station in Philadelphia.
I would guess that there would be many DVOA orienteers who would be glad to pick you up there and deposit you in the Pine Barrens...try writing the meet director. However SEPTA <
http://www.septa.com> probably has buses which would be helpful; and there is a PATCO speedline train <
http://www.drpa.org/patco> that goes across the Delaware River from downtown Philadelphia deep into southern New Jersey. But at some point you'd have to depend upon finding a ride to the meet site, since the Pine Barrens are quite remote.
And I wouldn't discard the idea of camping there too quickly. The last time I camped in the Pine Barrens, it was a surreal but enjoyable experience: very isolated feeling despite dense surrounding population centers, sandy forest floor, endless pines silhouetted in the moonlight...and drinkable water in the streams, despite its coffee-colored appearance.