I joined Toastmasters in April of this year (2010). I have had a lot of experience with public speaking and have no issues when talking to groups of people. But even with my love of public speaking have learnt so much it's almost unreal.
Toastmasters is great because it is a slow process of coaching and improvement. You get to watch others, listen to the commendations and recommendations and even have a turn yourself.
The safe environment of a club is great. Others in your club know how it feels and can mirror back to you both your good and not so good speaking habits and traits. Speeches are generally 5 to 7 minutes so the time is very manageable.
The first lesson I learned was the professionalism of a meeting. Every speech is timed, every member has a role or a speaking part and once the clock starts ticking everyone (should) act professionally.
Competitions are very interesting. There is a huge difference between speaking to give a speech and speaking in a competitive way. Even for the pro's the butterflies come out at competition time so Toastmasters is a great way to conquer your fears.
In our club we have one lady who has developed from not speaking to anyone at all - all the way through to being somewhat confident and able to stand in front of a group of people. I totally recommend Toastmasters as a professional development tool. For both the confident and the not confident alike.