1. Good old-fashioned press releases can still be very effective – if the media happens to pick yours up. Some newspapers do have event calendars and will include your event there. Note that some papers will only publish free events at no charge; expect to pay if you want your fee-based event included.
2. Online PRs geared toward SEO are also an option—though these generally have a price attached to them based on the topic and distribution.
3. Add the seminar to your Events page on Facebook and post about it (free). Ask fans to tell their friends. If you have the budget, run ads in Facebook targeted at the demographic you are trying to reach.
4. Include your event on your website with the appropriate keywords and make it easy to register. Then include a link to the page in your e-newsletter in a short article with details about the session.
5. Find a group whose members would have interest in the topic and ask them to promote it to their members. (LinkedIn is a good place to search for groups.) Optionally, partner with someone else whose interests are similar.
6. Add the event to meetup.com.
We know how hard it can be to get news of your event in front of the right people, but keep trying! You may have to test several channels to find what works best for you. If you have found a great solution, we'd love to hear from you. Good luck!