Tripoli Blood and Sand is a set of fast-play wargames rules for The Italian-Turkish War, 1911-1912, and Sanusiyya Revolt, 1912-1931, in 6, 15, 20, 25 and 28mm.
20th Century
Battle For 2mm Earth
Battle For 2mm Earth is a set of free wargames rules for pre WWI wargames in 2mm scale.
Morschauser Inspired Russian Civil War Rules
The Battle Game of the Month Blog has the outline of a set of free wargames rules for playing games set in the Russian Civil War. They’re inspired by Joseph Morschauser’s rules.
Life Issues Online 1936 – 1972
Google has the full text of Life magazine issues from 1936 – 1972. An incredible resource.
WRG Infantry Action 1925 – 1975 Rules
The classic WRG Infantry Action 1925 – 1975 rules are available free for the downloading. These are the June, 1972 edition of the rules. The link opens a pdf.