For those of you that have seen the NZ All Blacks perform their pre-game haka, here's a bit of info on it.

From Wikipedia http://en.wikipedia.org/wiki/Haka:
"A haka is a Māori posture dance accompanied by chanted vocals. Haka actions may include facial gesticulations such as showing the whites of the eyes and poking out tongues and a wide variety of body actions including slapping the hands against the body and stamping feet. As well as chanted words, a variety of cries and grunts are used. Haka[1] may be understood as a kind of symphony in which the different parts of the body represent many instruments. The hands, arms, legs, feet, voice, eyes, tongue and the body as a whole combine to express courage, annoyance, joy, or whatever feelings are relevant to the purpose.

Haka are sometimes popularly thought of solely as war dances, but individual haka have different purposes, not all related to war. War haka were originally performed by warriors before a battle, proclaiming their strength and prowess in order to intimidate the opposition. Today, haka constitute an integral part of formal or official welcome ceremonies for distinguished visitors or foreign dignitaries, serving to impart a sense of the importance of the occasion.

The word haka also has a broader use as a generic term for Māori dance or song accompanied by dance. A group of people performing a haka are known as a kapa haka (kapa meaning row or rank)."

The All Blacks Haka is also on Wikipedia:
http://en.wikipedia.org/wiki/Haka_of_the_All_Blacks