I found this on google by typing 'public speaking training' I couldn't really think of another way of searching for it but I'll admit I didn't exactly rack my brains to come up with this one
I don't know about internet forums, but you could try to find a local Toastmasters club. They will help you build confidence and speaking ability. I know someone who became an excellent public speaker from Toastmasters. I recently saw him give an impromptu speech at his own mother's funeral that sounded polished and prepared.