Chronofus has written a set of free miniature wargames rules called Piracy, and also an amazing amount of supplemental and source material on pirate captains, pirate history, pirate flags, nations of the Caribbean, slavery, clothing, weapons, currency, towns and more!
Chronofus has written a guide to wargaming the Aztecs. This is a major work, with information on the various troop types, and comes complete with color illustrations
The Warhammer English Civil War group not only has lots of information for fans of the game, it also hosts a number of Warhammer variants, including an American War of Independence version.
Has the “Darkest Africa” fad passed? I hope not. The Wargames Foundry line of figures by Mark Copplestone and others sparked a hobby-wide interest in miniature wargames that were more role-playing oriented — adventure games, if you will. If you’re still playing darkest Africa games — or if you’re thinking about getting into them, here’s a good site with historical maps of Africa.
This site has a good history of the Thirty Years War, with lots of of information about the various phases of the war — The Bohemian Rebellion, the Palatinate, etc.. Lots here that I never knew about.
If you’re interested in gaming the ThirtyYears War, there’s a post here about a set of rules for the period.