These are my favorites:
Peony for sit down dim sum (in the Renaissance Center, 2nd floor)
Tao Yuen on Franklin (just south of Renaissance Center) for the best "to-go" steamed bbq pork buns and other treats
Yung Kee (9th and Webster-across the street from Bank of Canton) for quick and cheap noodle soup, bbq pork and chow fun
I've been going to Sun Hong Kong - 7th or 8th off Webster - for over 20 years - best Hong Kong style seafood in the Bay-area. They have a branch in downtown Berkeley and in S.F. Chinatown ---- check out the clams in blackbean sauce or the chow shu chow mein (roast pork crispy fried noodles) Open until 2:00am.