The Mission Community Market on Bartlett Street between 21st and 22nd has re-opened again (Thursdays from 4 to 8 pm) and has expanded somewhat.
The vendors sell a good range of local seasonal produce (currently lots of lettuces, leeks, green garlic, carrots etc.). The strawberry vendor is particularly good -- usually offering different varieties.
New this year are 4505 meats (both cuts of meat and sausages) and a seller of ravioli.
The market is relatively small, so I wouldn't call it a destination. But if you live in the neighborhood it is an excellent resource.