I've been watching the anime, but I'm staying away from the manga for now, and I still don't quite understand the rankings... From what I can gather, the ranks are something like this:

Student
.....|.....
.Genin.
.....|.....
Chuunin
.....|.....
.Jounin.


Those are just the basic, overall rankings, though. There are other ranks, like ANBU, Sannin/Sennin (Three Ninja/(Legendary or Hermit) Ninja? The play-on-words is most likely intentional, since east-asian languges do it all the time, hehe.), Kage, etc.

From what I've seen in the anime, ANBU are most definitely at least Jounin. It seems like they are *ranked* as Jounin in the hierarchy, but are a special subset, a group that is either very good, or are trained specifically to hunt down "Missing-nin." Probably both.

The Sannin are outside of the hierarchy, but if they were within it they would at least be above Jounin level. Most likely they seem to lie between Jounin and Kage, if "Kage" is really considered the "top" level. Much more powerful than even the best Jounin, but for some reason chose not to be Kage or are not good enough/allowed to be Kage? Probably the former, since the pervert teacher (Ebisu, hehe) told Jiraiya that Hokage has been looking for them to help fight Orochimaru. You would have to be pretty damn good if people were looking for your help...

Kage is kage. I think everyone understands what it means by now. Kage are on an entirely different level than everyone else. Orochimaru is considered "kage" level, if not in name then at least power/skill.

If anything, the hierarchy seems to be like this:

Student
.....|.....
.Genin.
.....|.....
Chuunin
.....|.....
.Jounin. -> ANBU
.....|.....
[Sannin]
.....|.....
..Kage..


What do you guys think? I don't mind "spoilers" from the manga if all you're doing is clearing up the order... The anime isn't as clear as it probably should be, considering how much time they devote to flashbacks/rehashing/explaining things.