When I was young, I had what I thought was a phobia (they hadn't named disorders yet then) about being the center of attention in ANY situation. I was painfully shy, and even as young as grade school, if I was going to have to walk into class alone, I was absolutely terror-stricken.
I never took any drama or debate classes in high school because I knew I would never be able to muster up the strength to speak to a group.
In my 20's, I was working in an office where I was increasingly required to participate in meetings with a large number of staff. It wasn't too bad, however, because I was a department lead, knew everyone quite well, and most of my contributions had to do with training issues. So it was a given that they really wanted to hear what I had to say.
As I progressed through my career, I became more involved in Convention Sales and large groups. The hotel I worked at had a policy. At the first general session or major get-together of the group, the Salesperson in charge was required to welcome the group, thanking the company for its business. The first time I had to welcome a group, it was the American Grey Eagles - a very elite group of retired pilots that met every year. There were about 200 of them.
I was so frightened that I would choke up at the microphone. But as I walked through the room, I did exactly what Dorian suggested. I picked out the couple of familiar faces I knew (from pre-convention meetings) and I spoke to them. Although my arranged speech was only about 2 minutes long, it seemed like SO much longer and I felt very self-concious. I had practiced what I was going to say, however, so that helped ALOT - I was able to say what I needed to without much concious thought, and afterwards my Director patted me on the back and told me what a good job I'd done

That was like a trial-by-fire, and the fact that it went well helped me immensily. After that, I continued to give welcome speeches and officiate at Awards Banquets for golf tournaments as required, and it got easier and easier. The largest group I was ever involved in was over 600, an annual Bocce tournament that I handled for 3 years. I was a constant presence for the three days of their tournament, and presented awards, which entailed being on stage (with theater lighting no less) for 2 hours. It was just great!
It's been years since I've had to speak in front of a group, but it's something that I sincerely came to enjoy. Give it time, and put yourself in positions where you can practice - especially so you get used to speaking into a microphone. It will get more and more comfortable for you as time goes on.
Good Luck!