First of all, some very interesting theories. I like the idea that Harry is a horcrux, though I'm not entirely convinced, and I was also facinated about the possiblility of Dumbledore being a portrait. This would be extremely usefull, obviously, but might not help the general storyline...we'll see...
Anyway, this whole 'Regulus Black is R.A.B' thing fits quite nicely, and if you read paragraph three on page 108 in Order of the Phoenix, the cleaning crew find 'a heavy locket that none of them could open.' Could this be the horcrux that Harry and Dumbledore tried to get in the cave?
If it was a horcrux, then it will be hard to find, and they threw everything away. However there is a posibility that Kreacher stole it (if you remember he tried to retrieve items which were being thrown away) or possibly Mundungus (who Harry threatened outside the Pub when he found out he had been stealing from Grimmauld Place.
Finally, I refuse to believe that Snape is evil! I just wont believe it, i dont care if he killed the only person Voldemort was ever afraid of, and despises the person responsible for Voldemorts downfall, he is not evil, I'll beet my socks on it.
Ok, maybe I'm being stubborn and ignorant, but hey, I'm British, what can I say?
