Portraits of War, a fascinating study of war photography and the well-researched human stories behind them:
https://portraitsofwar.wordpress.com/

The Aerodrome, a fantastic resource for researching aviators and aircraft of the Great War:
http://www.theaerodrome.com/index.php

Doughboy Center, a single stop portal that immerses the reader into every major (and some pretty obscure) topics related to the American Expeditionary Forces:
http://www.worldwar1.com/dbc

Hell's Observer, possibly the most detailed firsthand account written in the field by an American soldier in WW1 ...or perhaps any war:
http://www.hellsobserver.com/

U.S. Militaria Forum, is the place to learn and share about anything and everything related to American military uniforms, equipment, weapons, photos, and more ....an incredible free resource: http://www.usmilitariaforum.com

Wehrmacht- Awards, is the German counterpart to the US Militaria Forum and the very best place to learn about authentic German militaria:  http://www.wehrmacht-awards.com/
Sharing some of our favorite links: