God Will Know His Own is a set of free wargames rules for “Knight and Crossbow era Wargame Rules 1096-1590(or 1789) then into the horse and Musket era.”
medieval
Medieval Market Floorplan PDF
Dramascape has a free medieval market pdf.
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.