Warhammer has been adapted to every period I can think of. Here’s a version called Warhammer Panzer Battles
Miniatures Rules
Franco Prussian War Rules
Natholeon’s Empires offers a set of free wargames rules for the Franco Prussian War.
Great Northern War Rules
Natholeons Empires blog offers a set of free wargames rules for the Great Northern War. Fought from 1700 – 1721, The Great Northern War was a conflict between Sweden and Russia for supremacy in central, northern and eastern Europe.
The Lights Are Going out WWI Rules
The Lights Are Going Out is a set of free wargames rules for WWI in 1914. The rules are designed for 15mm figures.
Eagle Rampant — Roman Variant For Lion Rampant
Eagle Rampant is a Roman Ancients variant for Osprey Games’ Lion Rampant rules for small scale medieval wargaming.
And an after-action playtest report.