Sengoku Jidai is a set of quick play samurai skirmish rules. There’s also a Korean supplement.
skirmish
World War II Skirmish Rules
The Tyneside Gamers offer a set of World War II skirmish rules. Lots of other rules sets at the page also.
Arquebusier Renaissance Skirmish Rules
Arquebusier is a set of free wargames rules for skirmish games set in the Renaissance.
Simply Skirmish Rules
Simply Skirmish is a set of free wargames rules for easy to play skirmish games. The author writes:
Simply Skirmish is a skirmish system based on GZG’s FMA game system and incorporates FUDGE concepts. It’s goals are a simple, easy to use skirmish system, suitable for table top gaming with up to around two dozen figures and is also suitable for Role Playing Games as well. It accomplishes this with simple, yet subtle, rules for combat that are easy to play and remember.
Basic Skirmish For Dungeon Hacking
Matt Lloyd offers a set of Basic Skirmish rules with dungeon crawl adventures in mind.