The Junior General offers a set of rules — and paper ships — for the 1571 battle of Lepanto.
David Heading offers a set of Renaissance Naval Rules.
Italian Wars is a set of free wargames rules for games set in the Renaissance.
Hot Trod and Red Hand is a set of free wargames rules for sixteenth century Anglo-Scottish border warfare.
Clockpunk is like Steampunk — except it’s set in the Renaissance. The science fiction sub-genre is set in a Renaissance where technology that was invented many years later comes into play. Here’s a new blog called DaVinci Automata dedicated to the genre. Plenty of ideas here — especially if you already (as many of us do) own Renaissance era figures.
I remember playing a game at a Chicago convention some years ago called DaVinci something-or-other that involved a large number of Leonardo DaVinci’s war engines. It was a lot of fun.