Clearly it's street-sweeping day:
To report sidewalk parking in SF, call DPT at (415) 553-1200
Hit 1 for English
4 for "more options"
3 for "sidewalk parking"
You'll need to catch the address in front of which the car is parked. It's stupid and unnecessary, but DPT won't send someone out unless you give them the exact address. Local activist Carleigh notes that this is a blatant violation of ADA laws, so maybe mention that if you're given a hard time.
Also, it's worth going back a few days later to everyblock.com, which lists police reports by location, to check on how your report was resolved. And if you like, take a picture and upload it to Flickr with "pedestrianist" as a tag. I'll post it here along with any resolution or notes in the comment section.