I used to be pretty nervous of public speaking but my degree program required a lot of public presentations so I was forced to hone my public speaking skills. Here are some of the things I picked up:
1. You can never be too prepared. Know your information and practice presenting it out loud and in front of a mirror. I usually outline my presentation on note cards in pencil and make changes while I am practicing. This helps you tweak the flow of the presentation and weed out stuff that sounds stupid. Practice a lot and you might even want to practice presenting more material than you are actually going to be presenting again, you can never be too prepared and sometimes you forget stuff.
2. Change your perspective. People aren't judging you. They want you to do well and want to be entertained. Think of it as an opportunity for you to speak your mind.
3. Relax before you start talking and take deep, focused breaths. Do not be afraid of uncomfortable silences(this includes when you ask a question and no one responds immediately). If you show your audience you are not afraid to sit it out and wait it makes them feel obligated to respond and shows that you are in control.
4. Eye contact. This is why it is important to know your information and not just read off of notecards or PowerPoint slides. Scan the audience and make eye contact. Address your audience, all of them, not the floor or the back wall. This is also a good time to give the hot chick you have been checking out a little extra attention, she'll notice and probaly give you a nice smile which can give you some added motivation and boost the energy level of youre presentation(note:this is optional). Alright, focus.
5. Never, ever say "I am sorry I am nervous...", ""Bear with me..." , etc. These are all negative and your audience is going to be expecting a bad presentation even if you do great. Not to mention, just vocalizing these negatives makes you impose them on yourself...self-fulfilling prophecy type of thing.
6. I like the idea mentioned by jnevin about exposing your genitalia...I have bailed myself out of many a stumbling presentations by saying, " Oh yeah, uh, yeah, well look at this..." and pulling out the tubesteak. It is an effective smoke and mirrors tactic that can be used as a contigency instead of tips #1-5