Warning: Scattered thoughts ahead...
Anyhow... Harry being a Horcrux was one of my first thoughts too, followed closely by Gryffindor's sword. I also thought that it may have become one in the Chamber of Secrets. The question is, did Tom Riddle's book transfer the Horcrux, so to speak, or was it somehow holding part of a soul to put in another Horcrux?
I, for one, was really hoping to have Fawkes come and just kind of perch on Harry's shoulder or something. I'm not quite sure why, it would have just been a nice touch to have Fawkes there as a kind of extension of Dumbledore. Also, maybe if Fawkes hangs around with Harry in the next book, somehow Fawkes could break the whole effect of the brother wands to help Harry kill Voldemort.
I'm still working with the whole Snape being good thing. I think Snape was actually looking into Dumbledore's mind during that pause in the tower, and Dumbledore's begging was him trying to get Snape to do just that, so that he would know what to do. I'm not quite sure what benefit Dumbledore's death would be at the moment, but I'm sure there is one. Also, Snape kind of protected Harry as he was escaping by saying that he was "the Dark Lord's".
EDIT: Oh yeah, and Hogwarts as a Horcrux WOULD be a great idea, nice one Shim.