Tercios Brevis Editio is a free version of the Tercios rules for the Thirty Years War.
thirty years war
Gott Mit Uns Thirty Years War Rules
Gott Mit Uns is a set of free wargames rules for the Thirty Years War. The author writes:
Gott Mit Uns (GMU) is a tabletop miniature wargames simulation of the Thirty Years War (1618-1648) that lets players refight the largest battles and seiges in a historic and enjoyable way, from White Mountain to Norlingen and beyond. GMU can be played with two players, one per side, but is more enjoyable and managable as team game, with one player per wing per side (1-4). The best miniature scale for the game is 10mm for visual impact, or 15mm. A 28mm game of GMU would require a very large space.
Thirty Years War Painting Guide
Vexillia has painting guides for the Thirty Years War in both pdf and epub formats.
Eye Candy: 28mm Battle of Lutzen
Eye Candy: Lonely Gamers has a set of photos of an absolutely fantastic 28mm game of the Battle of Lutzen from the Thirty Years War.