You might consider the CY a few blocks north of Dupont Circle. The rooms are smallish and the hotel isn't fancy, but the staff is excellent and it has one outstanding feature....

DC has building height restrictions (but for the Washington Monument and Qatar Apartment Building) and this hotel is at the edge of the first hill leaving downtown. The view is spectacular if you can get a room on the side of the hotel facing downtown and on the Hilton side of the hotel. (the SE corner of the hotel) It's one of the best views in the city.