Here are some subjects I am qualified to teach which could be interesting:

History of local industry (I am writing a book on it)
All about trains, historical and contemporary (I was a conductor and am a free-lance railroad journalist)
Comparative Religion (I teach this now for CCV)
Religious Questions (I can teach religion in an open non-sectarian way that allows students to explore)
Free-lance writing & Journalism (which I do, and there is no reason they can't also learn and submit for publication.)
New Media - ie blogs, facebook, etc and making them work for you (I've blogged since 2004)
Massage (I'm certified by Kripalu, teach massage at CCV and have led massage workshops for high school students)

These are all subjects that I'm enthusiastic about, but at another level what I'd be offering is myself.  I treat kids as individuals and also set limits and expectations.  My teaching style is experiential, aiming to multiple learning styles.  I am able to establish credibility, build community and inspire.