I am a HUGE fan of this site after spending a few hours reading many great posts about Spain and Mexico. I truly believe in the importance of good eating while traveling.
I lead a five week program in Spain for my high school and this will be my fourth year with that trip. We spend 2 weeks in Sevilla, 2 weeks in Valencia, and long weekends in Madrid and Barcelona. We have many day trips, but Segovia and Avila have a big food component. I thought I would give my best restaurants for these areas. I love good food and have a knack for getting some great recommendations from the locals. I would love to get feedback and more recommendations.
Sevilla: Bar Eslava, Bar Estrella, Casablanca, Cerveceria La Giralda, Al Medina, Coloniales
Valencia: L'Estimat, Cinque Lune, Horchataria Daniel, Galeria, Domestic (gourmet take-out), La Francesa del Carmen (by far my favorite restaurant in Spain both for the food and the owners)
Madrid (more places needed): Bardemcilla, Casa Paco
Barcelona (more needed): Asador Aranda, La Fonda (in the Olympic Port), Taller de Tapas
Segovia: Meson del Candido Avila: Went to Meson del Rastro going to give El Rancho a try.