I'll put in a plug for Toastmasters, which is a global organization which can help introverted people become less so. There is likely a nearby meeting or two you can find at www.toastmasters.org. It's low-cost, and you can usually visit for free to see if it's something you would like.

Briefly, it affords you the opportunity to give 5-minute speeches in front of a group in a supportive atmosphere. There are also shorter or longer speaking opportunities during the meeting, which often runs 1 hour.