Delta does not operate any international flights out of SFO, but there are a number of partner flights available. Since SFO is not a hub for Delta, the only domestic destinations are hubs (or focus cities in the case of Boston and Cincinnati).

Domestic:
ATL
BOS
CVG
DTW
JFK
LAX
MSP
SEA (mainline and regional)
SLC (mainline and regional)

International:
AMS (operated by KLM)
CAN (operated by China Southern)
CDG (operated by Air France)
GDL (operated by Aeromexico)
ICN (operated by Korean Air)
LHR (operated by Virgin Atlantic)
MEX (operated by Aeromexico)
PVG (operated by China Eastern)
TAO (operated by China Eastern)
TPE (operated by China Airlines)
YVR (operated by WestJet)
YYC (operated by WestJet)