Melanie Wong suggested I post what I know about this place for those of you who have been chasing Shanghainese eats all over the Bay. It's a place my wife shops at (or at least goes to to hang out with her homeys) on a regular basis.
San Yang (the name was "borrowed" from a famous old foodstuffs market on Shanghai's Nanjing Road) was long known as Metro Foods. When the Ningbonese owners of Metro Foods retired a year or so ago, the ownership and the name changed, but the stock continued much along the same lines. (I could add, editorially, that the stock rotation improved, along with the "vibes".)
San Yang has virtually no fresh foods, but specializes in packaged, dried, tinned and frozen foods familiar to people from the Shanghai region, including some hard-to-find stuff. We once ran into a Shanghainese couple there who said they regularly drive down from Portland, Oregon to pick up provisions they are homesick for.
A few examples of specialties which draw people to San Yang are:
-- Blocks of frozen uncooked kaofu, for those who like to prepare it themselves, plus the readymade tinned versions.
-- Bags of frozen "you mi jing" (the peculiar Wuxi specialty, airy golden-brown wheat gluten puffs that look a lot like fried tofu).
-- Real Shanghai eel (again, frozen) pre-shredded into stir-fry sized pieces.
-- Shanghai-style "nian gao" in various dried and frozen forms, including the long uncut blocks that you slice yourself to your desired thickness (my wife loves these).
-- Frozen yellowfish (what would a week without yellowfish soup be like?)
-- "Eight Treasure" and fermented rice desserts
All manner of tinned goods (like Winter bamboo shoots), many from the popular Maling brand; bottled pickled stuff for tossing into your "pao fan" (Shanghai's "easy" variant on jook); chili and other sauces; specialty candies; teas; noodles, etc.
It should be noted that San Yang tends to be a little pricey, and a lot of the stuff they have can be found at other Chinese markets (and 99 Ranch) if you know where to look. But it's an interesting one-stop collection of stuff you're likely to find in the pantries or fridges of families in Shanghai.
It's on the south side of Broadway, about midway between Stockton and Grant.