Nausicaa.net: Porco Rosso
http://www.nausicaa.net/miyazaki/porco/
Nausicaa.net is the best reference site for Studio Ghibli films. In its Porco Rosso page you can find an illustrated synopsis, the always fascinating FAQ, scripts, lyrics, etc.

Buta-Connection: Porco Rosso [French]
http://www.buta-connection.net/films/porco.php
This site is really good and I think it offers really interesting information. Aside from finding a very detailed illustrated synopsis and character profiles, it has other sections like a 2 page analysis of the film, a page detailing the film origins and a section dedicated to art technique of the film. In addition, there is a section dedicated to the planes in the film. I like this site a lot and I hope you will too.

Online Ghibli - Porco Rosso
http://www.onlineghibli.com/porco_rosso/
For those of you who haven't seen the film and eager to catch a glimpse of the movie, or for those of you just enjoy reliving the film again, you should visit this page. The page host pages of screen captures from Porco Rosso!

Porco Rosso On-Line [Russian]
http://porco.anime.ru/
A site full of Porco Rosso information. Even though I don't understand Russian, I still really enjoyed browsing through the site. It's a really really great dedication to the film.

Ichigo's Sheet Music
http://ichigos.com/animemusic/p.shtml
Want to play Porco Rosso songs on your favourite instrument? Then visit this site to download sheet music of songs from the film.

Nausicaa Flash Game
http://jarnik.sfkpalantir.net/nausicaa/
Play as Nausicaa, Kiki, or Porco Rosso in this flash game to calm down the angry Ohmus.