http://www.mangatutorials.com/
http://www.howtodrawmanga.com/howtodraw/tutorials_all.html
https://www.youtube.com/user/markcrilley#g/u
http://pandabaka.deviantart.com/gallery/#Tut
http://norli.deviantart.com/gallery/#Tutorials
http://kitten-chan.deviantart.com/gallery/#Tutorials
http://iruka-loves-kakashi.deviantart.com/gallery/#Tutorials
i hope these tutorial are useful, there are more of them but i'll edit them later....
enjoy and improve your skill....