Having had the pleasure of doing public speaking a few times, the thing that I have been told to do, that definitely works... pick a few people who you can make eye contact with. Then bounce between them while you are talking. Let everyone else become an invisible mass. If you pick the people you are talking to, it becomes more like a conversation to a very small group of specific people - rather than this mass of people.
This is why some speakers like to immediately start with a q & a, or a "hypothetical" question to kick start their talk. If someone in the audience asks you a question, then you are making eye contact with them, and directly talking to one person. As long as you maintain the eye contact, the rest of the room disappears.
Then as you warm up, you can move to more people until it becomes a non-issue.