Well, I was one of 3 lucky (or should I say unlucky

) people who had to give a speech at my high school graduation. In front of, oh... about eleven
thousand people. Yep, 11,000. I was already sad about graduating and leaving my friends, so think about trying to give a speech in that situation. Add that to the fact that I've always hated public speaking. That was not fun. Not in the least.

I too got choked up at a part, but what I did was take a lot of deep breaths and picked a random face out in the crowd way in the back. I couldn't see who they were, so it was like I was just talking to air. Calmed me right down (that and If I got upset, I would've been up there thaT much longer...). So, I would suggest doing something similar or looking up at the back wall when you speak.
One psych. professor I had last year told us to repeat any presentations we had that made us nervous or were emotional topics over and over again until you can get through it without getting upset. Kind of the same thing as if you would be giving a eulogy-- if you read something 5 million times beforehand, it kind of (in theory) dulls the effect the words have on you. Hope this is helpful; good luck!
ETA: I just noticed your speech was today, but maybe this'll help you next time.