There is a difference between shy and introverted. Shy means you are uncomfortable interacting with people generally, particularly strangers, whether one-on-one or in a group. Introverted simply means you are more comfortable by yourself or with one other person.
I think it is very possible to be successful in business as an introvert, but shyness will be an obstacle to success. An introvert (to provide a concrete example) might have no trouble closing the sale, as long as it is a meeting with one decision-maker and not a whole team at once. An introvert is often very good at relationship selling. Success in business is not always about being a visible leader – many F1000 CEOs are introverts, and I believe Jim Collins’ work (e.g. Good to Great) shows that introvert CEOs are generally more successful because (among other things) they don’t have the same ego to feed.
However, it *is* necessary to be able to speak in front of larger groups at least sometimes. I think the answer to this is Toastmasters. There, you learn how to do various kinds of public speaking, and you learn how to do it well without being nervous. Like many things, it’s all about getting used to it, and most people do not get the opportunity to speak publicly very often. This does not mean you end up loving it – it will be hard and sap your energy – but it will allow you to do it well enough to complement your generally introverted style of doing business.
Saying your piece in a group setting where you are not the “assigned” speaker is a somewhat different matter. I think the experience of Toastmasters and other public speaking will mitigate the discomfort somewhat, but not entirely. The real problem in this case is a lack of self-confidence. You may be afraid of ridicule, or of being wrong, or of getting into a debate with someone who has a strong personality and a big mouth. The solution consists of two pieces: appropriate filtering and appropriate handling.
Given that you are not inclined to just blurt out what you’re thinking, you should say something in a group meeting only when (a) you are pretty sure you are right, (b) you have something to say that is different than what everyone else is saying (that doesn’t mean you necessarily disagree – it could be additive), (c) what you have to say is important to the discussion. Oh, if only EVERYONE would filter this way, meetings would be a lot shorter. If you filter in this way, people will be less inclined to beat up on you, because they know you only contribute when it’s potentially valuable (they may disagree, but won’t be as harsh). Appropriate handling is how you position your thoughts. First, be explicit about your level of certainty (but don’t understate it just to hedge your bets). Second, don’t try to persuade, just try to explain. This is more objective and less likely to raise anyone’s competitive hackles. Third, as much as possible, position your thoughts as complementary to the preceding discussion rather than in opposition to it. This does not mean you should be Sarah Palin and *ignore* what was said before, and try to make it seem like you’re on the same page when you’re not. It means you should identify the points of common ground before you begin speaking and include them in what you say. Finally, if the bigmouth in the room *does* come back at you, you simply have to have a good response ready. My inclination, which is subtly sarcastic and wouldn’t work for everyone, is something like “why don’t we take it off-line and I can explain my thinking to you better.”
Shyness itself is simply a manifestation of low self-esteem. You can’t cure it by going to Toastmasters or anything else. Therapy, perhaps, can help with this. But you won’t be successful in business if you are shy. You could be successful as a worker bee, but not as a business person. Beyond a certain point of technical knowledge, business is all about dealing with people. We have different preferences with regard to how we deal with people (some people need to be in a group, some prefer one-on-one; some prefer to write and send email, others find it necessary to talk on the phone or in person). But if one is uncomfortable dealing with people, and in many cases in business they *will* be strangers, then I just don’t see how you can make that work. You have to believe that others will get value out of dealing with you – or they won’t.