Aircraft is one that springs to mind. Over the span of four years, aviation went from something like the [Taube] (http://en.wikipedia.org/wiki/Taube_monoplane) (a very primitive aircraft that played a crucial role at the Battle of Tannenberg) to advanced Fokker and SPAD fighter aircraft. These aircraft, were incredibly advanced when compared to what was flying in 1914. World War 1 and World War 2 were two great quantum leaps in aviation, which is to say the least a pretty important development, and not only militarily.

And then there's the tank, first introduced during World War 1 in 1917 by the French and the British. Very important military development, but I'll leave it to someone else who knows more about them to fill in the details.

According to a show on NPR last week, which I believe is this one, radio technology was hugely boosted by the war. In addition to its obvious effects on the battle field it has had a pretty unmistakeable effect on public life. In particular, the return of men who had been trained to operate radio equipment led to the proliferation of radio broadcasting for news and entertainment post-war.