Add to this fun Chain Bridge Road off of MacArthur (steep and rough, and a nice break from the tedium that is MacArthur Blvd). You could also add Loughboro Road to this mix, as the climb past Sibley and up to AU is a nice grind on smooth pavement.

And if you head out of the District toward Great Falls on MacArthur, there's Walhonding Rd (into the Mohican Hills development) or Mountain Gate Drive. The latter is a leg and lung burner, and makes a nice loop with another steep shot, Brickyard Road (again, off of MacArthur).

As a bit of a shameless plug: the PPTC "Downtown Breakaway" rides, which run every Tuesday evening starting in April, use a lot of these climbs (not the Rock Creek Park ones, save for the "Summer Solstice" variation) to get good miles in a limited time frame (limited by sunset). I'm one of the leaders of this ride, and it's a good way to get good training miles on a weeknight, starting and ending in DC.