One of the things we want to do for Tech Ed New Zealand this year, is raise the quality of local speakers.
We might set some hard goals around this - something like local speakers must score 7.5 or higher on average to be asked back next year. Nigel and I have talked about this, but we haven't decided wether we will or not yet (feedback welcome).
Anyway - if you want to raise your own game, find and attend a toastmasters club near you. I found toastmasters really good for raising the awareness of what makes a great presentatin - even though I never finished the course.
For a listing of New Zealand clubs - go here and select your area/town (middle of the page on the right).