World War 1
Worldwar1.com: Trenches on the Web: Big Guns of the Great War
This site from Trenches on the Web gives an overview of the different types of artillery used in World War I. Provides several thumbnail images of rail guns, howitzers and other forms of artillery, which can be enlarged by clicking on them.
World War 1
Worldwar1.com: Trenches on the Web: Armory: Artillery
Data covering the types of standard and heavy field artillery used by both sides in World War I.