Lord Merlin has a set of free wargames rules for large (70mm or 1:20) scale figures. There are three levels to this skirmish rules set: “simple”, “better” and “more realistic.” There also are some cute pictures of a “knights of the dinner table” game.
medieval
Wars of the Roses Skirmish Rules
The Cool Guy or Dweeb site offers a set of Wars of the Roses skirmish rules.
Internet Medieval Sourcebook
The Internet Medieval Sourcebook is a fantastic resource for miniature wargamers. I’ve had this one in my bookmarks for several years and haven’t even begun to plumb its depths. The section on the Crusades is particularly useful.