Having lived in San Francisco for the last four years I thought that by now I would have gotten my first decent earthquake out of the way. But alas, I am still an earthquake virgin. So I walk around with the question looming in my head, "When will it hit & then what the hell do I do?"
Luckily enough, the San Francisco City Government has my back. It just implemented a new system where people can sign up their cell phone numbers and will be notified in the event that an earthquake, tsunami, or Mutant Robot Attack hits the Bay area. In addition to alerting you of the impending natural/unnatural disaster, the SMS service also will instruct people on what to do afterwards.
You can sign up here: www.alertsf.org.
San Francisco gets SMS earthquake alert system [Textually.org]