A while ago I mentioned a group called Toastmasters as a way to improve public speaking skills.
Wait, I'm talking to preachers, they already know how to speak in public. Right? Preachers know how to preach, but public speaking on a topic other than the bible with a time limit of 3 to 5 minutes is a different game. Being required to speak extemporaneously for 30 seconds to a minute with no warning is different.
As preachers we are called by God to speak the eternal truth of Scripture into the lives of people. But we are also professional speakers. Sometimes we need to strip away the bible stuff and just work on our craft of speaking.
I strongly recommend that you go to Toastmasters - it's a great way to hone your craft (and you can emphasize a new skill like telling stories or jokes), it's a great way to meet people, and it's a great way to get out into the community.