Co-incidently Craiglist was a question earlier this week on Who wants to be a Millionare. Something about which city it was formed or started in. San Fran area I believe.
Yep, it was San Francisco. They have a small office in the Inner Sunset area. Coincidently, that is the area you will find most of the micros in the city. It is right on the N/Judah trolley line.
Craigslist is not bad if you are planning to travel out of town, but for me, it has not produced any results in Vancouver, maybe because I have found many better sources (PERB, eg).