Kings of War is a great free fantasy rules set from Mantic Games. Here’s a variant for the Viking Age
Rules: Dark Ages
Pigs and Glory: The Viking Sagas
Pigs and Glory is a set of free wargames rules for Viking Saga Campaigns. It is designed to give some context to period battles.
Solitaire Song of Blades and Heroes
Dougi has a set of adaptations for solitaire play of the popular commercial set of rules Song of Blades and Heroes.
Argad Medieval Skirmish Rules
Argad is a set of free wargames rules for skirmishes in the dark ages and for pirates in the 17th and 18th centuries.
Ravenfeast – Norse Saga Skirmish Rules
Ravenfeast is a set of free wargames rules for skirmishes in the Norse sagas.