Previous posters have hit the high points. Let me add a few personal favorites. These are joints you dont mind walking in alone with a book.

Three resturants in Lake Anne Plaza are good. Il Cigno most expensive, Montmartre cheapest. All 3 have al fresco dining on the lake. Bands on Thursday.

El Manantial (sp?) in Tall Oaks Plaza, and Zefferelli's in Herndon are iDine.

Shahi Kabob in downtown Herndon. Go for Chicken Karahi.

Tara Thai in Vienna (iDine). Go for soft-shell crab or crispy fish in chilli sauce.

Nizams in Vienna. Better Doner Kebab than I had in Istanbul.

Clydes in Reston Town center. Again, sit outside and watch the kids on the plaza, or sit inside and watch bigger kids picking one another up.