I have been on some blog talk radio programs and I feel that blog talk radio programs are a good resource to increase exposure for any activity. The best way to draw an audience is to have information which people are interested. The next option is to generate information on numerous sites that offer options for promotional opportunities such as the ones you mentioned. In ning.com there are a host of sites that may offer opportunities to promote your program and your publisher. I would also participate in networking forums such as this site related to the topics to be discussed with a link to your program.
I agree with Dennis. I would also recommend to make sure you add the site to your business cards and give it away to people you network with offline also. Depending on your show you can also link up with associations in your area or organizations in your community who reaches your particular audience. Get them involve in your show. The more people you get involve the more they will be likely to spread the word of your show. Shoot for influencers, people who are popular and are hot items in your area. Exchange links with sites and shows that are similar to yours. Those are some ways to help you build an audience fast.