Euro Bistro on Elden has some vegetarian pizzas and pasta dishes. Herndon also has a lot of Thai restaurants, so you may want to do a Herndon search on the DC board to get recommendations. Are you looking for ethnic or more mainstream food? For mainstream fare, Reston Town Center is nearby and has added some better chain restaurants that may work, such as Il Fornaio -- you'll want reservations for that one because it's popular. If you like Indian, Angeetha on Elden is also good.
i'd suggest this be moved to the washington, d.c. board.
mayuri indian in nearby reston has delicious food. http://www.mayurimahal.com/home.html
meat dishes and veg dishes are quite tasty. the buffet lunch is outstanding. the food is fresh and good quality.
we were introduced to it by indian friends who like good food.