There are many myths around public speaking anxiety. One of these is that public speaking anxiety is bad for you. It can in fact increase your level of performance and make you come across better to the audience. In fact it is normal for an audience to rate the speaker’s performance much higher than the speaker themselves.
Here is a great video that discusses the myths of public speaking anxiety and provides information on public speaking. The sound quality isn’t great but it is worth persevering with.
The Confident Speaker by Larina Kase and Harrison Monarth is well written and will help people to speak confidently in front of groups of any size. It is great for beginners and people finding advancement in their careers been held back by their fear of public speaking.