Welcome to Maryland/DC and the mid atlantic region, based on your post I see you are from New Hampshire.
I hope you left your snow tires and frostheater back home
(except for maybe 10 days in the winter when it hits the 20's the frostheater is useless. When it snows, everything shuts down schools and all)
Although not a TDI Gtg in the purist sense of it, tomorrow though there will be a big VW GTG at Impex in Baltimore county, similiar in size and scope to some of the big TDI GTG's hosted at Impex in years past.
http://forums.vwvortex.com/zerothread?id=4313716
So if you are into VW's and Audi's and want to get a taste of the Maryland VW scene come on out, I am 99% sure there will at least 10 TDI'ers there along with some of Maryland's best cars, tuners and mechanics.
Also don't forget we have the 2nd Largest GTG in North America at the end of this summer called H20 in Ocean City, which although riddled with drunken debauchery sillyness and sunburns, it is a blast and 100% Maryland.
As you can tell, I am really proud of where our state/Region is at.
As far as I know, the TDIfest in Philly was the biggest, but always the TDI ImpexFest had 100+ cars (eclipsing most TDIfests in attendance numbers).
The only Maryland is missing, is Chris Hill (MrChill)