The Wargames Table has a nice article on modeling trees for The Great War. The trees also look to me as though they would be nice for a deadlands type of fantasy setup.
World War I
WWI and WWII Naval Rules
Steve Burt offers a set of free wargames rules for WWI and WWII Naval combat.
Making WWI Airplanes From Clothespins
This post on making WWI aircraft from clothespins is not really a set of instructions, but the photos show clearly enough what has to be done. Brilliant bit of model making.
The Light Horsemen (1987)
A fictionalized account of the Australian Light Horse Regiment in Palestine in 1917.