Here's some tips for calming yourself down about speaking in front of others. First, practice like crazy. Familarize yourself with the material. Give your speech in front of a mirror a few times so that you can see that you look fine while giving your speech and you wont feel like a fool while you're actually up there. Give your speech in front of friends and family. Have someone else read your speech aloud for you, and you can see where you want to put in gestures and emphasis, and fix any parts that seem slow or dry. A few days before the speech, go to the place where you will be giving it, and try practicing it there. If it's busy, just go stand in the place where you will be giving the speech and visualize quietly to yourself. That way the shock of standing in an unfamiliar place will be gone when you actually have to speak for class.
Before your actual speech, do some speaking exercises to loosen up your vocal cords and fine tune your enunciation. Your professor will probably give you a few of these exercises in class. While giving your speech, instead of saying um, take a breath or a pause. Make an effort to talk slowly; it always seems slower to you when your speaking, but faster to others.
The most important thing about giving a speech is to remember to BREATHE. I know it sounds dumb, but I've judged a lot speech competitions where people are so nervous that they try to rush their speech in one breath and forget to breathe and turn red and get flustered.
Good Luck!
I've had to do a lot of it in grad school, and I still suck the big one, but it really does a bit easier with practice. Unfortunately, that's the only way to work on it. There's a group I've heard about, Toastmasters, with chapters in lots of places where you can get together with ppl and practice. Still intimidating, but sounds really helpful. 
