Middle Ages Easily the Best Site on the Internet for Middle Ages. Includes topics of Feudal life, Religion, Homes, Clothing, Health, Arts and Entertainment, and town life. Has many small interactive sections.
Medieval Fiefdom This site has great information about a Fiefdom and the people that live there.
Internet Medieval sourcebook A wealth of Information on numerous topics from the fall of Rome to the Reformation. If you can't find something about the middle ages look here.
History of Western Civilization – a college course with a series of lectures on various topics.
Castles, Sieges, Knights, and Combat
Nova: Medieval Siege Life in a Castle, an overview of siege technology and a castle wrecking game make up this site.
Castle Learning Center Everything you wanted to know about Castles and the people who lived in them.
Battle of Hastings Great Information about this pivotal battle as well as what came before and after. William the Conqueror information here as well.
Medieval Warfare Everything you need to know about castles and how to defeat them as well.
Code of Chivalry Information on the code and conduct of knights.