Medieval
A Coat of Steel
War of the Roses rules like you've never sen before, ten years in the making.
Advanced Wargames Rules
Advanced wargaming rules for generals who want actual games rather than the luck of the dice games I see so so often.
Aegir's Fire
Viking campaigning rules - usable with any set of skirmish rules and any scale, this set contains strategic rules for raiding, developing your viking crew and some exploring. Ideal for someone with lots of different figures from the period.
Age of Blood 2nd Edition
The idea behind the rules is to allow you to play good sized skirmish games using 28mm scale miniatures from the likes of Gripping Beast and Foundry.
Alexius
A quick and easy campaign game for the Crusades period in the Byzantine Empire, including map, counters, and miniatures interface for the Ironbow rules. 
Away With Honour
Medieval Naval Warfare, inspired by the excellent medieval ship range from Outpost Wargames Services. 
Axemen and Allies
A Medieval miniatures variant of Axis and Allies.
Bad Endings
A simple set of Medieval Skirmish rules, not for the feint hearted by Craig Cartmell.
Battle of Agincourt (1415 AD)
Fast play rules for the famous battle.
Battle of Hastings
Rules for the Battle of Hastings.
Battle of Hastings(2)
Fast Play Rules for the famous battle.
Battle of Hattin (1187 AD)
The Crusader army was dying of thirst when they approached Lake Tiberias only to find Saladin's army blocking their path.
Battle of Liegnitz (1241 AD)
In 1241 the mighty Mongol army launched an invasion into Europe.
Battles of the Barons
This simulation is about feudal Europe from 700 AD - 1200 AD, the late Middle Ages. The simulation is not set in any specific part of Europe, and the term "baron" is used to refer to nobles.
Battle Troll
Man to man combat as depicted in the Icelandic Sagas.Free Scenarios .
Chevauchee
An easy-to-learn tabletop game designed for play with medieval miniatures and inspired by the popular Skirmish system.
Comitatus
A complete set of wargames rules designed to simulate warfare in Europe and the Mediterranean from about AD 250 to 1100. They have been primarily designed with Barbarian Migrations period in mind but the scope of the rules covers Dark Age warfare through to the period of the First Crusade.
Crusader
Crusader is designed to represent small-scale actions during the 11th to 13th Century. It is intended to be simple and fun - any relationship to historical reality is purely co-incidental.
Crusader Lite
Lite version of the new Crusader Minis rules suitable for Saxons and Normans.
Danegeld and Dragonships
Dark Age Skirmish Rules Playtest Version.
Dark Age Infantry Slog
Andy Callans demo rules for the medieval period originally published in Miniature Wargames, No. 7, 1983.
Dark Age Rules
Simple Dark Age Rules (They are in fact a scan of the original rules - but in poor quality).
Dark Ages
This was published a while back in Practical Wargamer, however, it has been improved and speeded up since then. It is suitable for Medieval skirmishes, too. 
Day of Battle III
A miniatures rule set that allows you to raise and then lead an army of soldiers in the Feudal period. Ground scale is very low at just 5 yards to the inch. Units are usually made up of 3 bases with a unit representing 50 to 100 men Uses DBx basing. 
Fast and Furious
Is a set of 1:1 simple, fast and fun rules for ancient and medieval skirmish scale games using 25-28mm or 1/72 plastic figures, and designed to cover roughly from 3000 BC to 1400 AD.
Feudal Warfare
1:5 scale Feudal-era rules for 25mm size figures. It is taken to be roughly A.D. 750-1250.
Field Of Honour
This is a simple two player card game that is an abstract depiction of two ancient armies facing each other on the battlefield. It can either be played as a simple two player card game, or as a sub-game to a more complex wargame.
Foray
Skirmish rules for longbow wars derived from Man-at-Arms. Join the Yahoo group to download.
Free Company
Being rules for small actions of the Hundred Years War and other fights of the longbow era.
From Macbeth to Medici
These rules cover the period which saw the rise and fall of the mounted knight as the primary combat arm, and as such are all about charging about the place in a disorganised manner, haranguing your allies and subordinates.
God's Acre
This edition of God's Acre was published in the United States by Heritage Models Publishing Division in 1977. It's not entirely as published.
Guts
Dark Ages and Fantasy Combat System Craig Cartmell. 
Hawkwood
Rules for the later Middle Ages based on Ancient and Medieval Warfare. 
Heimskringla
Viking Naval Warfare in the Age of the Sagas.
Into The Dark
Using old fashioned game mechanics to create a Medieval mass combat game system that's fast, simple and easy to play.
IronBow
Miniatures rules for the Crusades era. The ebb and flow will determine the victor. (Requires Princes of the East).
Joust
Simple Jousting game for knights.
Knighthood
This is the third edition of Knighthood that was published in 1992. It was the final version that used six sided dice. It also was the last version of the “bucket of dice” game.
Knights and Knaves
A skirmish level game of combat in the Middle Ages. Extra scenarios and rules for naval, sieges and campaigns are also available.
Knights v Knights
Simple rules that use simplified combat using a a coin.
Lord Merlin's Rules of Engagement
These skirmish rules are designed around the use of large (c. 70mm or 1:20) scale figures. Smaller figures will work, of course, you just have to adjust some measurements accordingly.
Lords and Levies
Fastplay medieval card driven rules, 4th in our series!
Lords and Levies: Siege Rules
Siege rule expansion for Lords and Levies.
Mayhem: Warrior Kings
Man to man combat in ancient and medieval times from Two Hour Wargames.
Medieval Battle Rules
Brian Cameron's Medieval Battle Rules for 25mm figures.
Medieval Castle Siege
Rules to recreate a castle siege.
Medieval Clash of Armies
These rules are based on Fast Play Rules for Students (Medieval History) by Matt Fritz.
Medieval Period Rule Set
Fast play rules.
Medieval Siege
Medieval Siege is played with two or more teams.
Medieval Skirmish Rules
One figure = one man one inch = 10ft one move = about 30 seconds.
Medieval Skirmish Rules
Fast play skirmish rules. Originally created for Wars of the Roses games.

Medieval Skirmish Rules
Quick play medieval rules. 
Medieval Skirmish Rules - Leaders and Duelling
Add on for the Medieval Skirmish rules.
Medieval Warlords
These are rules for a large-scale play-by-email campaign, for up to 23 separate realms. There is a map provided for the historical time period circa 1320 AD.
Men At Arms
One brain cell medieval skirmish rules for 25mm figures.
Metalsmashing
Quick and simple rules for the Ancients and Medieval period.
Mindstalkers: Mission Middle Ages
A 3D skirmish wargame usig 3 to 4 figures each. From the homepage you can also download factions or "Vexillia".
Miniatures Combat
This is a fantasy medieval skirmish combat system that is intended to
work for narrative style games where there are heroes fighting anything
from rank and file minions to Cave Trolls.
Minimal Melee Combat
Minimal Melee Combat is a simple game designed to create a feeling for combat between to combatants armed with swords. It is not designed to be an accurate simulation and make no attempts at this.
Monjoie
Monjoie! is a set of skirmish rules designed to provide an entertaining wargame based on the Song of Roland. The rules are intended for use with individually based 25mm/28mm figures with players controlling one or two heroes and their retinues.
MudGrunt
Medieval modification of Ground Zero Games' StarGrunt II rules, written by Jon Tuffley. They require you to own the StarGrunt II rules.
My Kingdom for A Horse
Each player controls one or more retinues. Each Retinue consists of a Lord, and a group of men sworn to defend him.
Pigs and Glory:The Viking Sagas
A set of rules to create interaction between families of Vikings and to give a purpose to all the mindless slaughter.
Princes of the East
A political/military game of the period immediately after the first crusade. Each nation strives for supremacy. Only the strongest, most cunning, will leave a legacy of stabilty and survival for his people.
Rebellion
28mm Skirmish rules for the Scottish War of Independence led by William Wallace in 1297. Now expanded with cavalry, archers, pikes and heroes.
Rules By Ral
A modified version of the rules that Ral Partha used to hand out at conventions and which were on their web site till recently. All units are 12-man infantry or 6-man cavalry units.
Saxon Dogs
The author finished reading Bernard Cornwell's Arthur trilogy, and discovered Gripping Beast's fantastic 28mm range of Dark Age figures and obviously there was no way that he could resist.
Shields and Blades
This rule set is a squad-level scale using side move / countermove system. The rule set has opportunity fire (with both standing and moving fire). Since these rules are not skirmish level, the shield facing and facing of the castings is not a problem.
Shieldwall
Shieldwall aims to recreate the atmosphere of Dark Age battles in the British Isles and Northern Europe. The rules were inspired by Andy Callan's Dark Age Infantry Slog.
Siege of Kenilworth Castle (1266)
The simulation is a matrix game, and for the most part follows the standard matrix game rules.
Simple 100 years War Rules
Eric Woods' one-page (front and back) rules for Medieval games. From a former Jackson Gamer.
Simplus Minituris Rules
Simple Medieval rules.
Skirmish
A cardgame of dark ages combat in similar style to Lunch Money by Atlas Games.
Skjaldborg
A largescale skirmish set for Ancient and Medieval wargames. Can also be used to fight bigger battles.
Standards of Valor
Phil Pournelle's Standards of Valor Dark Ages rules based on Stargrunt II.
Strategike Antiquity medieval periode
A DBA like rules. Quickly and easy to make his army. In French.
The Rules According to Ral
These rules were originally published as by Ral Partha.The medieval battles described in these rules are fought between armed groups of men led by valiant leaders represented by miniature figures.
Tourney
Knights of old prepare to match your skills of battle on the Tourney. Defeat your opponent in the Joust, win the Lady's favour, and triumph in the Grand Melee. Only then will you be worthy of the title 'Knight'. Lots of extras on the Homepage.
Viking Raid Rules
Viking raiding rules fun game for 3- 4 players
War of the Roses
25mm Skirmish wargaming a touch of influence from Retinue, the best of the commercial Wars Of The Roses rules.
Werod
A set of warband level rules for the Dark Ages. It covers the Age of Arthur through to the Norman Conquest and allows you to use the tactics of the period, shieldwalls and svinfylking. The current version is available for playtesting.
White Steeds and Seax
An adaptation of Dark Age Infantry Slog that now inlcudes Cavalry which were not in the original rules.