If you're travelling out to Fairfax (gleff's suggestion), I haven't been here in a while but a favorite was Westfields Marriott. They did a Sunday brunch that was huge. It was always worth the money. They take over one of their larger ballrooms every Sunday and put on a huge buffet with all of the expected stations, including carving, seafood, omelette, etc. Their pastry chef always seemed to have a great time with their dessert time and the many options.
Reservations are recommended.
14750 Conference Center Drive
Chantilly, Virginia 20151 USA
Phone: 1-703-818-0300