Black Hat Miniatures offer Four Musketeers, a set of skirmish rules / scenario in which the Musketeers must retrieve the Queen’s earrings.
Arquebusier is a set of free wargames rules for skirmish games set in the Renaissance.
Blood Guts and Glory is a free RPG with a unique setting: Elizabethan Post Apocalypse:
Blood, Guts & Glory is a mash-up game that takes two specific out-of-print editions of a different games and blends the rules for the two games together, using the best elements of each system. For legal reasons, neither of the the games nor their editions are named anywhere within this site or within Blood, Guts & Glory itself. However, this doesn’t matter. If you know the games then you will pretty much instantly recognise them, and if you don’t know the games then it doesn’t matter – you can play Blood, Guts & Glory on its own merits.
By default, Blood, Guts & Glory is set in and around a post-apocalyptic Elizabethan London. The human race is extinct, and Elizabethan society is now populated by the various animal folk that have inherited the Earth.
However, the game can be played in any fantasy setting with little to no modification of the rules (and such modifications are suggested in the book itself).