Alan Saunders offers Great Northern War, a set of free wargames rules that he describes as:
A heavily modified version of the Horse & Musket/Pike & Shot rules in Neil Thomas’s ‘One Hour Wargames’ specifically for use with the Great Northern War.
Great Northern 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.