1. Contribute to discussions on blogs that relate to your metro area
2. Contribute to forums that relate to your metro area, and put the website in your signature
3. Submit your site to "directories of directories"
4. Post ads on your metro area's Craigslist, offering free ad space on your site. Offer one spot once a week. (Don't know if this is against T&C but worth a shot if it is.)
5. Slightly more expensive but you can try Facebook advertising. That way you can target locality, age, likes, gender, etc.

I think starting a blog to supplement your directory site. Write about the things that are going on in your area and maybe highlight certain businesses/events. A good way to promote your site would be on Twitter. You can target people who have given their location as your area and start up conversations with them.

I agree with JW about facebook. Their new systems for ads makes it REALLY easy to target very specific demographics. For instance you can market directly to 23 year olds in Portland if you wanted to get that focused. I have heard about a lot of people that have had success using FB for focused local ads.

Everyday I see an ad for the same golf course in my area, and I have clicked on it more than once over the last year.

Craigslist would also be a good bet, but harder to reach a specific demographic inside the target area.

Anyways thats just my 2 cents...