Chez Spencer - Fourteenth at Folsom is the approximate locus of two culinary stars. One is Rainbow Grocery where you can find an amazing collection of exotic and exciting foodstuffs (but no meat or fish!). The other is Chez Spencer which, though it is hidden in a small industrial space on a pretty gritty street, is one of the best French Restaurants in the city. The chef works from an open hearth kitchen in the middle of the space, and live music comes from the piano near the front windows. The food is classic french, with things like roast squab, rack of lamb, foie gras, and butter, butter everywhere. When it isn't raining, you can sit on the entrance patio under some heaters. Recommended
Clouds - Located at the top of Yerba Buena Gardens, Clouds looks past its landscaped rooftop garden out on the city skyline, This is a place probably not visited much by San Franciscans, as it is off (and above!) the beaten path. However, it is worth seeking out if you are in the area (maybe on a trip to SF MOMA), as it is a pleasant enough place, and great for lunch on a sunny day. My lunch was "Seared Ahi Tuna with mizuna salad, crispy bean noodles, soy-sesame syrup, green onions, wasabi cream and pickled ginger" for 8.95, which was a good deal. This isn't a destination restaurant, but keep it in mind if you are near SF MOMA, the Metreon, or Moscone Convention Center. Recommended.