Here are just a few links to some sites worth exploring. Most of the best sites out there are in Japanese. I haven't actively searched for sites to put on this page so if you know of a site that should be mentioned here please contact me.

This site was recently mentioned in an article for nationalgeographic.com
"Neogeography" Blends Blogs with Online Maps

English Sites:

Castles of Japan
This site features over 100 castles in English with pictures. A unique feature is that he posts the commemorative stamps you can get at most sites. The site author also maintains an active Facebook community.

Castles of Kyushu
Well designed site that focuses on the castles of Kyushu as well as the people and events that shaped its history.

Japanese Castle Trek
Very cool Quicktime and Cubic VR scenese from several castles in Japan. To get a good understanding of what it is like to visit a Japanese Castle this site is a must see.

Oshiro Meguri Fan
This is the English page of the Japanese site listed below. The English content is much more limited than the Japanese site, but it is still very good.

Samurai Archives
In-depth research page on Japanese samurai and history.

Castles of Japan
Pictures and basic information for about 30 castles.

Castles of Japan
Thinkquest site with a number of my own pictures. Well designed with much information.

Himeji Castle: Virtual Tour
This is a great "virtual tour" of Himeji Castle by way of pictures. It also allows you to look at a map and choose the direction in the castle you wish to follow. Check it out.

Japanese Sites:

Oshiro Meguri Fan
This is one of my favorite castle sites. It has a great many pictures of castles and information about every aspect imaginable. It even has pictures of the grounds where castles once stood and their histories. A very nice professional looking site.

Oshiro no Tabi Nikki
Guide to over 750 castle sites in Japan. Contains pictures, explanations, and useful information for visiting the castles. This is a site I always check before visiting a castle.

The Photograph of a Castle
A guide to hundreds of Japanese castles. The site includes castles from all over Japan with very detailed coverage of the Nagoya/Tokai area where the author lives. I really like that he includes the architectural structure and type of donjon such as bourougata and renritsushiki where available.

Azuchi-jo Quicktime VR
A very cool site with Quicktime VR scenes from Azuchi Castle.

Kamon World
The most comprehensive site about Japanese family crests and the histories of some families in Japan. Kamon World provided the family crests you see with the castle profiles on this site.

Worldwide Castle Sites:

Medieval Castles of the World
Castles of the world organized by country.

Castles of the World
Reference for castles, palaces and monasteries around the world.

Castles on the Web
Contains links to everything on the web that's even remotely related to castles. Mostly European focused but they do have a page of Japanese Castle sites. You can also Rate my site here.

Topcastles.com