DCHenge is Tonight, September 23!
Reminder: this evening, the sun will set in exact alignment with the lettered streets of D.C.'s grid. While "DCHenge" may not rival the Manhattan Stonehenge, early scouting suggests that you could glimpse a pretty nice sunset along corridors such as L Street NW:
It depends on the weather, of course.
Photo of the sunset on Sept. 21, 2009 by Will Atwood Mitchell, Creative Commons Attribution License