These are the best Harry Potter sites that have come to my notice. Kudos to them all! (If you want to add your HP site here, e-m@il me [sarbarajbartaula(at)yahoo(dot)com] and if the site is really good, I'll put the link here. For now, the sites are:

www.jkrowling.com
This site belongs to the mastermind behind it all, J.K. Rowling. She is the writer of all Harry Potter books (as if anyone didn't know). This site is really cool. You ought to visit it sometimes.

www.harrypotter.com
This site is the official homepage of Harry Potter movies and belongs to Warner Bros. Cool place to get latest info on Harry Potter movies (apart from here).

www.emmawatsonofficial.com
This site is the official Emma Waston. Cool place to get latest info on Emma. It is a very newly built site.