Visit this article http://www.bytestart.co.uk/content/legal/people/bullying-at-work.shtml for bully defense advise from a legal perspective. While some of the advise is important to establish patterns of bullying, be cautious about writing letters to bullies without the backing of the administration.
Here’s a quip from the article that I do favor-waiting out the storm: If you are being shouted at by your boss my advice is to wait until the storm has passed, repeat your concerns back to him/her and be specific about how to fix things. Distill the issues discussed in the outbreak. Your boss will expect you to be defensive or to break down, but instead make sure you communicate that you’re a supportive employee and you’re on his/her team.