1) Call in to a local radio show to pitch the new content – in SF, we have a guy who does a 30-second open mic show. Like a free ad.
2) Buy a targeted Facebook ad, with a design aimed at bringing people to the site based on impressions, not clicks. Read more here.
3) Ask all of your friends who have Facebook accounts to post a blurb about the site on their pages. Ask your target audience to do the same. For example, I have more than 500 facebook friends (my three audiences – friends from church, SF politics, and Gov 2.0), so when I post something to my news feed, it gets a lot of eyeballs.
4) Use a Twitter account to search and identify locals and others in the target audience, then blast out a unique promos for the site once a day. My site gets the most hits when I promote something to my Twitter group, which is mostly Gov 2.0 and social media folks.
5) Make a short video on YouTube or Tokbox, and promote that link through e-mail and all the channels above. Consider making it a very memorable video that people will want to share.