One of the Ferry Building [1] mainstays, the Acme Bread Company (1 Ferry Plaza, #15, 415/288-2978, Mon.–Wed. and Fri. 6:20 a.m.–7:30 p.m., Thurs. 6:20 a.m.–8 p.m., Sat.–Sun. 8 a.m.–7 p.m.) remains true to its name. You can buy bread here, but not sandwiches, croissants, or frou-frou pastries. But the bread you’ll get tastes better than just about anything west of Paris.
The original bakery was the brainchild of Steve Sullivan, who began his baking career while working as a busboy at (where else?) Chez Panisse in Berkeley [2]. To this day, all the bread that Acme sells is made with fresh organic ingredients in traditional style. Beware: The baguettes are traditionally French, so they start to go stale after only 4–6 hours. Eat fast!
Links:
[1] http://www.moon.com/destinations/california/san-francisco-and-the-bay-area/sights/financial-district-and-soma/ferry-building
[2] http://www.moon.com/destinations/california/san-francisco-and-the-bay-area/east-bay/berkeley/food/fine-dining