Use E-mail marketing.
Ugly, but effective for the cost. Blast out your special offers, but be nice about it.
Use off-line marketing.
Promote your site. Put your url on all your license plates. Paint it on your car. Buy newspaper and yellow pages ads with your url. Put up flyers and stickers. Sponsor a little league team. Do anything and everything to spread the word about your website around your city.
Run regular promotions.
Stage regular giveaways and spread the word about it.
Get published.
Write articles for publication on other websites. The author profile will link to your site. The article will show that you're an expert.
Publish yourself.
Write articles for your own site regularly. This will help you to win on the search engines and gives your visitors...