The Gode Cookery site contains so much more than cookery. There is some clip art (A feast for the eyes), many menus, and a glossary of cooking terms. They even have a channel on YouTube. The original receipt is given as well as a modern redaction.
Medieval Recipes collects material from several cooks and several countries. Lists of recipes by category include those that travel well, those that are easy, and those that are vegan. The original recipe is provided as well as the modern redaction.
Cariadoc’s Miscellany contains many recipes, collected over many years. The Miscellany itself contains lots of other topics and opinion pieces by an SCA pioneer. It’s a great place to visit if you have a weekend or three to spare. He links to the archive of the SCA-Cooks mailing list, just in case your time is infinite.
There are many books and websites that perpetuate the myth that medieval cooks used lots of spices to disguise the taste of rotten meat. If a book or website tells you this, toss it in the trash right away, and read Daniel Myers’ article called “Drummond’s Rotten Meat”. It’ll be hard to read with your computer in the trash, but it’s worth it.