Theory on Dumbledore
There's a site someone kicked up on a blogger, and on it the lady has REALLY gone into one of the ideas from the book. She says it was brought on by a chat originally started at a Barnes & Nobles chat, by Cathy of TLC.
She goes really into detail, and it's quite the interesting read.

Cathy Liesner's theory is that Snape has done just what he said he could do: He has "stoppered death" for Dumbledore. And I believe her theory answers a lot of questions -- and it does so without creating a lot of "Yeah, but what about--" responses.
Cathy proposes that what Snape did for Dumbledore when he returned to Hogwarts was "stopper" death: Postpone it, but not indefinitely. This theory answers the question: What happened to Dumbledore's hand? In every scene where Dumbledore appears in HBP, our attention is drawn to that blackened, burned hand. Why, we have to wonder, hasn't Dumbledore fixed it? Well, what if he couldn't? What if he's lucky to have that blackened hand -- because the only other choice was death?We see support for this in the Dark curse that struck Katie Bell. Dumbledore reports on Katie's prognosis shortly after the curse:"...She appears to have brushed the necklace with the smallest possible amount of skin: There was a tiny hole in her glove. Had she put it on, had she even held it in her ungloved hand, she would have died, perhaps instantly. Luckily Professor Snape was able to do enough to prevent a rapid spread of the curse--""Why him?" asked Harry quickly. "Why not Madam Pomfrey?"A rapid spread of the curse. Hmm. Could that be what happened to Dumbledore? He reached Snape in time for Snape to prevent a rapid spread of the curse laid on the Ring Horcrux, a curse that, in Dumbledore's own words, would have killed him -- but Snape stoppered that death.
Have a moment online? It's definitely worth the read, so check it out HERE.