I think the best hills in the area are Glebe or 123 up from Chain Bridge and Tilden St in NW DC up to Connecticut Ave from Rock Creek and then continuing up to the Cathedral.
Alexandria has some nice ones, not the scale of the 123/Glebe area but enough to get your heart pumping - Russell Road runs near the bottom of a hill, turn right (if headed south) up Mansion Drive or any of the side streets into the Beverley Hills area.
