public speaking

I have never had to speak in front of a lot of people, but I don't think it would bother me all that bad. I have spoken in front of classmates which includes all of 20 people, but other than that, nothing much. I have always wanted to be able to give a speach to thousands of people, but I think that would be a little intimidating. My biggest strengh is that on most subjects that I know well, I am able to get my point across and most of the time, I'm very convincing. My biggest problem with public speaking is that I dont have a very good speaking voice. I seem to have a problem with mumbling a lot, and that makes it hard to understand what I'm saying sometimes, and my voice doesn't travel very well, so I don't get heard very well, but other than that I look forward to talking in front of the class, and I am not uneasy about it at all.