Castle Posters at AllPosters.com
Castle Books at Amazon.com

DMOZ open directory section on castles
http://search.dmoz.org/cgi-bin/search?search=castles

Definition and explantion of castles at Wikipedia
http://en.wikipedia.org/wiki/Castles

Visit Camelot
King Arthur's Home The Ultimate Destination
http://www.camelotcastle.com/

Castles on the web - a collection of links to castle resources
http://www.castlesontheweb.com/

Castles of the World
http://www.castles.org/

Castles-of Britain.com Dedicated to the study and promotion of British Castles
http://www.castles-of-britain.com/

The Castles of Germany
http://www.mediaspec.com/castles/

Ian's Land of Castles
http://inside.bard.edu/academic/specialproj/darling/castle/castles.htm

Historic Irish Castles
http://www.historic.irishcastles.com/

Roads To Ruins - Guide to Castle resources on the web
http://www.roadstoruins.com/

Castles for Sale - also listing of castles to rent, tours and more
http://www.castles-for-sale.com/

100 German Castles - German Medieval Castle Hotels - Nice site, lots of information
http://www.germancastles.com/

Dark Isle - Castles, Manors, and Abbeys of Scotland
http://www.darkisle.com/castles.html

3D Photos of Castles and Fortresses
http://www.3dphoto.net/stereo/world/topics/castles/castles.html

Castles of the Middle Ages
http://www.medieval-castles.net/

Medieval Demographics Made easy - Numbers for Fantasy Worlds
http://www.io.com/~sjohn/demog.htm

Great Castles - A Journey into Europes Medieval Past
http://www.great-castles.com/