Seneca Creek State Park is about 7 miles from the Shady Grove Metro station in Gaithersburg, MD. Beautiful setting, 27 mostly-technical holes, short and long tees. I have met several people who found their way to Seneca during business trips to DC. Baskets are mostly in the short positions at the moment, so you might want to play long tees if you want more of a challenge (well, more of a challenge than hitting tight, wooded fairways).
If you rent a car and drive to Baltimore, I highly recommend Patapsco Valley State Park (especially the Green Monster course – long tees to C pins). You could spend a day playing the various permutations at Patapsco, with two tees and two permanent baskets on each hole. Rockburn Branch is another challenging course about 20-30 minutes from Patapsco.
I am headed to Patapsco in a few minutes to test out some new plastic. If you are around next weekend, let me know and I can try to show you one of the courses.