I am sometimes particularly nervous about presentations, either because I don't feel as confident about my content or because the content is particularly controversial. I've recently found a way to remove most of that stress: go to a climbing gym and climb to the top a couple of times. I've done this twice recently, once before giving a talk at the Central APA and once today before being a guest speaker (well, mainly, grillee: they read my paper and questioned me after I gave a brief synopsis of my ideas) at an undergraduate class on sexual ethics. Both times I had the experience that after climbing the nervousness about the presentation mostly went away. And when I sensed it coming back, both times all I had to do was to call to mind a vivid memory of holding on high up and I relaxed immediately and the nervousness went away again. The memory of recent physical effort and accomplishment combined with the recent illusion of danger made tough questions from an audience just not seem like the big deal that they otherwise would have. Particularly at the APA talk, I also felt that my presentation quality went up significantly: I think I was more fluent and dynamic.
I thought I'd share this solution. There are probably many others of a similar sort.