I also sometimes get "phone shy." I resist calling someone I need to call. It is usually someone I don't know, and it is usually when I need to ask them for information or (worse) do something that I need to have done.
One technique that I've found helpful is to actually script the conversation from my end. I write out who I am, why I am calling them, and the questions or requests I need to relay to them. That usually gives me the clarity and confidence I need to make the call. When I have a particularly bad case, I also just follow the script during the call. That way I make sure I don't hang up and then realize that I should have covered additional items.
I'm pretty sure this won't be of help to folks like taxgeek, who are chafing at the amount of work a properly conducted call creates. But it might be useful to others.