from a guy who got his stolen bike back:

I had my bike stolen from the bike rack at my dorm in Spokane (a city with a metro population of 600,000). It was locked with a cable lock (rookie mistake) and I didn't have the serial number (rookie mistake #2). That night I called the police and campus security and gave them a description of my bike. The next day I made a craigslist missing ad and posted it to surrounding cities and I left a flyer at my LBS. About two or three weeks later I got a call from the police. They busted a guy that was a suspect in large scale bike theft and he happened to be riding my bike at the time. They found my ad on craigslist and contacted me. I described the bike to them and got it back.
Just goes to show that you aren't totally out of luck. Just get the word out and keep your eyes open. Best of luck!