Think about it...what is the absolute worst thing that can happen?
What's the worst that could happen?
My pants could fall down.
I could throw up ... again.
I could forget how to speak.
I could forget how to walk.
I could have a stroke and start babbling backwards in Latin.
I could accidentally call down a plague on the audience.
"What's the worst that could happen" is a terrible way to approach a fear. The whole problem with being afraid is that "the worst that could happen" is only limited by my imagination and the more imaginative I am, the worse "the worst" could be.
I'm very uncomfortable speaking in front of groups, but when I've had to do it, only two things have helped: passion and preparation. For one, I have to really feel strongly about what I'm going to speak about. Of course, I don't often have the opportunity to speak to people about something I don't care about, so that's not a big deal. The preparation is a bit harder. One of my big fears about public speaking is the fear of saying something stupid. The best solution for me is to know as much as I possibly can about the subject I'll be speaking about so that I can come to it with much more confidence. It's tough to know everything there is to know about a subject, but there's always a point where I know enough to worry less about being taken by surprise.
The other thing that I've learned is to not even acknowledge being shy or uncomfortable. Just put that in the "nobody's business" category and get on with the matter at hand. Even if you turn bright red from everyone looking at you, don't pay any attention (which is always tough for me, since I always feel like I'm about to catch on fire when I'm in front of a crowd).
There's nothing at all rational about the fear, but I find the less power I give it, the less of an effect it has.