The Boy Who Drank Stars: Links

Howl's Moving Castle: The official English site for the film, at Disney.com. Includes a short biography about Miyazaki, a film summary, images, traliers, and US theatrical showings.
Hauru no Ugoku Shiro: Official Japanese site for the film.
Le Chateau Ambulant" Official French site for the film.
Howl's Moving Castle: Official Korean site for the film.
Il Castello Errante di Howl: Official Italian site for the film.
Liikkuva Linna: Official Finnish site for the film.
Diana Wynne Jones: The official website of the author and creator of Howl. It includes news and information about her publications, answers to fan questions, and personal information. The author, unfortunately, hasn't updated it for a while, but it still has lots of interesting information.
The Many Worlds of Diana Wynne Jones: Another official website of the author, maintained by her publisher. Features book summaries and excerpts, news, and a short biography.
Studio Ghibli: The homepage of Studio Ghibli, the animation studio that created the film. [Japanese]

Orca: A Japanese art site with some truly spectacular Howl fan art. The artist has works for both the book and film continuums.
Merry go Round: The only other Howl shrine I've ever seen. Sadly, most of the download do not work, but it does include a couple of pieces of anime-style fan art.
Chrestomanci Castle: Diana Wynne Jones: Dedicated to the author. It includes book information, links, quotations, background on the author, as well as a page dedicated to the Howl film.
Nausicaa.net: The most extensive website about Studio Ghibli on the web today. Features information about all of the various films of the studio, with news, summaries, reviews, availablility, and links to online media such as trailers and clips.
Online Ghibli: Another Ghibli fan site. Includes one of the few online galleries for Howl.