This is a great episode of the Human Weapon that talks about Ninjutsu...its pretty kick ass.
Ninjutsu (忍術?) sometimes used interchangeably with the term ninpō (忍法?) is the martial art, strategy, and tactics of unconventional warfare and guerrilla warfare as well as the art of espionage purportedly practiced by the shinobi (commonly known outside of Japan as ninja).
While there are several styles of "modern ninjutsu," the historical lineage of these styles is disputed. Some schools and masters claim to be "the only true and legitimate heirs" of the art, but ninjutsu is not totally centralized like modernized martial arts such as judo, karate or taekwondo. Togakure-ryū is said to be the oldest recorded form of ninjutsu dating to the 1500s.
Anyway you look at it....its a pretty kick ass martial art....seriously who didn't want to be a ninja at one point.