How to close a speech
Tim Wilson has a useful set of suggestions on how to close a speech. One of my favourites, that he doesn't mention, is to leave with a challenging thought. It could be a question, but doesn't have to be. It should produce "an ah-ha moment" or a smile from the audience, of understanding and agreement.
Here’s a site with some great information about Public Speaking:
http://www.nosweatpublicspeaking.com/