@joanna
<<Charlie appearing to Hurley: I think he is supposed to be really Charlie speaking from the beyond somehow... >>

I disagree with this...Charlie is an Island manifestation just like Christian in that the both of them are both doing the Island's bidding. The Island also had both Charlie's and Christian's (and Yemi's!) dead brains to analyze for their contents, to say nothing of the minds of the other Island dwellers who knew them, a la "Solaris". Also, how else would Charlie know about Christian going to viist Jack if he weren't a fellow Island manifestation?

<<Eko's brother seemed like a manifestation because of the smoke and his extreme bitchyness.>>

Agreed. He was there to stand in judgment of Eko, and Yemi would be the one person from Eko's past from whom he might have accepted that judgment.

<<Hurley's asylum pal seemed like a manifestation from his own head..>

Also agreed...just perhaps amplified or solidified somewhat by the unique properties of the Island.

<<Walt appearing to Shannon and acting weird seemed like a projection of his image from some remote viewing/sending station>>

Actually, I took that to be Walt projecting himself from the Others' boat upon which he'd just been kidnapped, given his rather moist state and his backwards-talking (which I took to be symptomatic of a combination of his relative inexperience with his abilities plus the mental stress of having just been kidnapped by the Others).

Walt appearing to LOCKE, however, was clearly either a Walt from the future doing the Island's bidding (he's gotta come back sometime, after all!) or else an Island manifestation (given his use of the "work to do" phrase that seems a hallmark of Island manifestations...).

<<Claire in the cabin - Can't decide.>>

I'm still going with :alive but following the Island's "white rabbit" down the rabbit-hole into Wonderland. ;-)

<<Anthony Cooper's appearance was convincing because we have confirmation he had mass and breathed and bled like a real person.. but I bet the island can make a clone if it wants to, so I am undecided on him, too.>>

Nah...that was the real Anthony Cooper. He was most likely brought in at Ben's behest to set Locke up for failure and nip in the bud any possible chance of Locke taking over the Others. Ben had to know as soon as he had the info that John Locke's was on the Island from Ethan that he was dealing with a possible "usurper", especially knowing what we know now about both Alpert's and Abaddon's interest in him literally from birth.

Here's a thought...perhaps the Island was telling Ben that he needed to accept Locke as his replacement with the tumor followed by a spinal surgeon also falling from the sky on Oceanic 815. ;-)