Join a nearby Toastmasters club. It'll give you tons of practice in speaking, and you'll quickly see how it affects your speech, not just in speaking contexts, but in any context where you have to speak to, communicate with, or lead people.
2 years into a Toastmasters club in Shanghai China and I have seen remarkable transformations among my fellow members. So many introverts have flourished under the program and gone on to be officers in the club and speech contest winners at various levels all the way up to nationals. Its really wild to see personal growth happening right in front of your eyes over the many months. Give it a try!