One of the most interesting people I've seen present is Damian Conway. He gave a talk in the Monday morning session of LCA 2006 called "Presentation Aikido" which talked about some of this stuff and more - unfortunately I then went out to a couple of other sessions which violated his points grievously. He then proceeded in the afternoon session to give a talk about the upcoming features in Perl 6, where he broke one of his own rules by talking for four hours straight on one topic. The thing that convinced me he was a good presenter is that he had everyone's attention the entire time and even I, though struggling, was able to come up with ideas and questions and take-home points three hours in.
His keynote on the technical and social lessons from Perl 6 development was epic, and worth watching just for his presentation style.
I later asked him where he learnt to present so well, and he said that he hadn't done any courses - he'd just observed what worked and what didn't in other people's talks and did more of the latter and avoided the former. I think that's one really good thing for every presenter to ask themselves: go to other people's presentations and ask yourself what you like about this presenter, what things they do well and what they do poorly, and how you can improve your talks as a result.