If you truly want to practice your public speaking skills, one of the best ways to practice is to go to a non-technical public forum with an audience (a public lecture with Q&A - NOT a local government meeting) and try to say something (it helps if you have passion/conviction on what you are saying) in a concise yet convincing matter.
Toastmasters also rocks. I got my CTM years ago - advice is to find a club that is not affiliated with your workplace or anyone you really know (more freedom to fail without feeling self conscious)