The San Francisco Bicycle Coalition has some tips.  Here's some more:

• You can file a theft report online with the cops. Or, you can call 415-553-0123.
• Post the bike as "STOLEN" on craigslist
• Post messages to bike-related lists, groups you're a part of.
• Monitor eBay, craigslist for your bike.
• Drop off flyers at Bicycle shops around town.

Super sketchy places that have stolen bikes

You should pay careful attention to places that are notorious for selling and having stolen bikes:

• Flea Markets
• Civic Center plaza
• Shops that have a reputation for selling sketchy bikes:
  • Karim Cycle in Berkeley