Youtube
youtube ^^
You could try YouTube but 4Kidstv is the best and free place to watch it. I think they have all yugiohs.
youtube
All (or at least almost all) yu gi oh episodes are on youtube
at 4kidstv.com
on youtube.
on youtube
4kidstv.com
I watch them on Veoh.com
youtube go to the 4kids channel
Hulu.com