I had a really hard time sharing at meetings as well. I brought up a topic one time about my having such a hard time sharing at meetings, and how fearful I was. The response I recieved was overwhelming... I'm certainly not alone in feeling this way!
I continue to bring up topics, listen alot, and it's getting easier and easier to share once in a while.
I also try to do more readings during step meetings or during the opening of a meeting. It breaks the ice, and gives me my voice while the nerves seem to melt away.