Dale Carnegie says that the secret to being a good conversationalist is to be a good listener. People like to talk, especially about themselves (and I don't really mean that in a bad way). If you are a shy person, ask questions that don't have short, dead-end answers (so no questions with binary yes/no answers) and you can "steer" the conversation while the other person does all the "peddling." ;)

I highly recommend Dale Carnegie's classic How To Win Friends and Influence People. The title turns people off, but it is a classic "people person" book.