If you have written on a topic that lends itself to presenting a public seminar, you might consider doing one for free at a local venue such as a library. In so doing, you are letting others know that you are a professional in your field and you’ll likely sell some copies of your books while you’re at it. And you never know. If you get a good response, you might find yourself setting up paid seminars!
You should also consider teleclasses. A couple of place on the net that you might try are Teleclass International and Teleclass.com.