Trevor Brabyn has posted The Galleon and The Flame, a Sword and The Flame variant for land and naval battles in the age of Drake and Hawkins.
This is just more evidence to support my contention that — if miniature wargaming has a standard — it’s Larry Brom’s The Sword and The Flame. There are more variants of this rules set than I can count.
Lion of the North is a set of free wargames rules for battles set in the Thirty Years War. The rules set also includes Haiduk and Rajtar for period battles in Eastern Europe, and a set of army lists.
Voyage! is a stand-alone campaign system for games set in the Caribbean during the mid-late 16th century. It is intended for use with the The Perfect Captain’s Spanish Fury game.
Hot Trod and Red Hand is a set of free wargames rules for sixteenth century Anglo-Scottish border warfare.
Archipelago of Gold is a set of free wargames rules for use with the constructable, collectable Pirates of the Spanish Main ships from WizKids. From the BGG description:
These rules use the Pirates of the Spanish Main and a hex map to allow you to explore wild islands for gold, build large fleets, settlements, cities, forts, and train your crews to become superior gun crews. Get more gold back to your settlement, and you can build more than your opponents.