Ninjai is one of my favorite flash based web animations, made between 2001-2005. I used to have copies of all the movies saved on my old computer but sadly lost those when it crashed. Their website has been down for a long time but fortunately they have it backed up on you tube.
Kill Bill 2 mentions it as it's suppsed to be one of B.B.'s favorite bed time stories, and is playing in the background. (along with lone wolf and cub) A little violent for a young kid, but hey it's Kill Bill afterall. Back in 2008 they announced they had teamed up with Tarantino to make a movie length version of it but there's been no futher info I've seen. However he's begun production on Kill Bill3, which I'm dying to see.
The first couple episodes are fairly rough but the animation does improve drastically as the series progresses. The music is largely from Jet Li's Twin Warriors movie which is one of my favorite kung fu films.
Anyways here are the compiled links as You Tube's search menu blows chuncks.
Chapter 1
http://youtu.be/U1iTFxTrhdgChapter 2
http://youtu.be/O7eN4-iJHTwChapter 3
http://youtu.be/1bTdapwmCSEChapter 4
http://youtu.be/8K-1tSS7lKYChapter 5
http://youtu.be/20HBzNMztiwChapter 6
http://youtu.be/2lirjpm2zhIChapter 7
http://youtu.be/olvya0CASWIChapter 8
http://youtu.be/xIih84g2GLIChapter 9
http://youtu.be/QbRMD-AUWbcChapter 10
http://youtu.be/aagpwNmCO0sChapter 11
http://youtu.be/FzIqeC3ewqQChapter 12
http://youtu.be/7_zOgnFlykY