Harry Potter for Nerds
BOOK 6 SPOILERS INCLUDED IN LINKED ARTICLE
John Granger has written another piece on the Alchemical Skeleton of Harry Potter.
I personally think that Alchemy does its level best to turn Christianity into a mystery religion, which doesn't make sense with the whole 'truth shall set you free' thing.
That being said, many of Granger's theories have come to pass in regard to the books thus far. There is a lot of further talk dissecting the books along these lines at Harry Potter For Seekers. Much of it makes my head hurt, but it is fun for those days when you want to immerse in Potter Arcana beyond 'shipping and slash.
In a semi-related note, the geekworld is speculating about book 7 being released either on 7/7/07 or 7/31/07 (Harry's & Jo's birthday)