ohh yes those are my favorites... even made a ringtone and sms sound from the chant :-D

An other good series is Ergo Proxy (very dark and gritty)

Deathnote is really good series as well (and can be found as manga books fairly easy... if you are in to that kind of Manga)

Lain - Very strange and psychadelic series, but mesmarizing... and is only 13 episodes.

Manga movies I can recommend (along with alot of the previous posters examples):

Tekkokinkreet - its pretty tough and cool as two street kids fight for their turf against yakuza and hitmen... Very wel done and has alot of details in the drawings and background compared to alot of other Manga.

Perfect Blue - Manga Noir murder mystery.

Paprika - also very strange and psychadelic but very well drawn and its captivating and wierd (in the good way) :-D