The overriding prinicple in dealing with an aggressive person is to never, ever lose your cool.
I have always found that when dealing with an aggressive person, particulalry someone who is being verbally loud or abusive, an effective tactic is to reduce the volume of your voice. The louder they become, the calmer and quieter your responses should be.
Practically, this compels most people to reduce the volume of thier voice, simply so that they may hear your response. Further, by not raising your own voice in response, you avoid engaging them in "the game" - generally most people begin to feel quite silly once they realise they are throwing their weight around and it is having no effect.
Clamness and quietness does not mean that you should become meek however. Maintain eye contact with your subject, and use thier first name when speaking to them. No sound in the world is sweeter to a person than hearing their own name. It is a subtle yet effective way to command the attention of a person, and compel them to at least listen to your message, without having to raise your voice.
Assert your right to be treated in a way which you permit, though do not mistake the manner in which a criticism is delivered with the validity of the criticism itself. It is possible that somebody may have an entirely valid criticism of you or the way in which you conduct yourself - but are unable to communicate thier dissatissfaction without recourse to rage. In this instance it should be communicated directly to them that the manner in which they are addressing you is unacceptable. Attempt to understand the core issue behind their anger, without responding to the negativity of the way in which they have decided to express themselves.
Will try to make a hub on this - nice question!