White Mountain is a hex and counter board game for the Thirty Years War. It’s designed in the vein of the popular Command and Colors system.
From the Godfather of American Wargaming, Jack Scruby, comes the Rules For A 30 Years Wargame. We have the people at Historifigs to thank for offering these free reprints of classic wargames rules.
Tilly’s Very Bad Day is a set of free wargames rules for the Thirty Years War. They are designed as a fast play set.
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.