The last thing you say to the audience is powerful.  Drive home your meaningful message with:
- Visual - something that provides a powerful picture that is a metaphor for your speech point
 - Bookends - end the speech in the same way you began it (e.g., if you open with a story, close with the same story)
 - One more thing - Steve Jobs made this closing famous by giving an additional announcement after all the regular announcements - make sure this announcement relates in some way to your speech topic
 
Ending,
Tim Wilson
Professional Speech Coach
Free speaking tips at: http://speakingquicktips.blogspot.com