You might want to check out the stickied threads at the top of this forum... especially THIS one.
In brief, Budo Taijutsu is the method of body movement and self defense taught by Maasaki Hatsumi, the current soke or head of several historical ninjutsu systems, combined into the Bujinkan. He hasn't been teaching the individual schools so much as a combined interpretation of them for the last few decades. He's focused on the lessons for life and combat contained in the principles of armed and unarmed combat within the schools rather than all the "other stuff" that fits popular conceptions of "ninja".