Got good content on your website? Share it. Have your listeners include your station widget on their My Space, Twitter, or Facebook page. It's easy. I set up an account at Widgetbox, designed my widget, and the software produced the code in short order. There also a ton of already-created widgets that can be customized and placed on your website.
Here's a promotion idea:
Have a listener widget page on your site. Creativity counts. The more creative the better. Maybe encourage listeners to share their favorite songs, favorite club, new movie, or summer activity. Whatever. Put your listeners front and center and make them a part of your community. You could even run a contest to see who can create the best and most creative widget.
Do you already do this? Share it with me and I will feature your website here on this blog. Got a better idea? I will be glad to give you props in this space too.