Now that I have finished reading HP7, I finally let myself go around and see what others are writing. Here is some of the best I found so far, to be read only if you have finished the book (or do not care for spoilers).
There is a paper that looks at sociopolitical aspects of the books.
And there is tons on the internets, e.g., this enormous comment thread on Pandagon, which touches on everything from quality of writing, through gender issues, to politics.
And there is a bunch about science of Harry Potter
And the greatest spoiler-full spoof of the seventh book, scene by scene. Hillarious.
I leapt in late at Pandagon. I personally didn't care for book 7 as much as I would have liked, for three primary reasons that I go into at my site. (Spoilers!)