Well, there is a thread here on mths and so forth.

Well I think, Orochimaru went into the Akatsuki to get the 8 tailed demon. He left because he couldn't get the sharingan from Itachi, and he probably wanted this before he got the demon, or before Itachi got his demon. Orochimaru can most likely get the demon on his own anyway. Orochimaru's plans seem to be, get the sharingan, learn jutsu, then get the demon at the same time, or just information on where it could be or something. If in fact he's still going after it, which I think he would, just because of how he is.

Using the descriptions from XanBcoo post.

One tail: Shukaku, I find it weird that Deidara's demon was this one, I would've thought he would go after the seven tail. Sasori would've been a likely candidate here also.

Two tails: I'm going with the leader type person for this beast, I dunno why, just feels like that.

Three tails: This demon represents Kisame the best, and would be the likely candidate.

Four tails: possibly Sasori, but he's dead now.

Five tails: Itachi, because of the illussions.

Seven tails: I would've chosen Deidara for this demon, because of the clay.

Eight tails: Would've went with Orochimaru

Nine tail: It seems that Itachi is after Kyubi, but that just might be because of him knowing of konoha, and Naruto. Although, Itachi was kinda pissed at giving Sasori to get it.