National Mall:
Lincoln Memorial
MLK Memorial
WW2 Memorial
Washington Monument (AKA Pencil)
Capitol Building
White House
Museums:
Air and Space Museum
National Art Gallery
African-American History and Culture (you'll need tickets way in advance)
National Museum of Natural History
Cava Mezze
2940 Clarendon Boulevard, Arlington, VA 22201, (703) 276-9090
Amazing small plate Mediterranean food in Arlington.
Boqueria Dupont
1837 M Street Northwest, Washington, DC 20036, (202) 558-9545
Really fun Spanish brunch. They even have breakfast paella.
Tatte Bakery & Cafe
2805 Clarendon Boulevard, Arlington, VA 22201, (571) 312-8691
Great breakfast, pastries, and coffee.
Caboose Commons
2918 Eskridge Road, Fairfax, VA 22031, (703) 663-8833
Local brewery with good beers and bar food.
Farmers Fishers Bakers
3000 K Street Northwest, Washington, DC 20007, (202) 298-8783
Good brunch/breakfast spot at Georgetown waterfront.