The internet is crawling with good sites for any subject. Below I have listed some of those I think is among the better - mostly with focus on WWI naval warfare.
A newly made wiki exclusively about HMS Warspite
Stunning 3D renderings by Mark Brown of the mighty battlecruiser HMAS Australia
All the World's Battlecruisers
Great site - lot's of photos
A fantastic community site in honour of the men of HMS Hood
German Naval History
Wonderful resource for the German navy for several eras.
A lot of information on naval weapon systems from all ages.
Viribus Unitis 3D Project
Fantastic website about the Austro-Hungarian battleship Viribus Unitis - great artwork.
World War 1 Naval Combat
Very nice site with detailed description of all major battles for the last century
World War 1 Document Archives
3D Warships der Kaiserlichen Marine 1871-1919
Yet another great site about the Great War
A fantastic website of the German navy. The details are absolutely stunning.