There were two main traditions in the European martial arts of the Middle Ages and Renaissance: German and Italian. While they shared some common elements, they differed enough that I would advise a student to master one or the other tradition well first before attempting to become competent at the other.
At the same time, both schools were trying to solve similar problems and did exchange ideas, so some knowledge of the Italian school might be of value to a student who wishes to master the German, and vice versa
AEMMA Primarily study the Italian tradition, as well as I.33, but their online library covers a broader array of resources.
ARMA They have a useful collection of historical manuals. Their interpretation of the historical evidence is often very, very unreliable.
The Chicago Swordplay Guild. Studies the Italian tradition.
Forteza Studies the early masters: I.33, Ms. 3227A (AKA Doebringer) and Fiore
The Higgins Armory Sword Guild German and Italian material, as well as later sources and a speculative attempt to reconstruct Viking combat.
HROARR"This site focuses on different aspects of Historical European Martial Arts." Articles on a wide range of sujects, and manuscripts from the German, Italian and Iberian schools
This group is dedicated to the study of medieval martial arts. We focus particularly on the teachings of Liechtenauer as interpreted by Döbringer, Ringeck, and von Danzig, and we also rely heavily upon Le Jeu de La Hache and Talhoffer, although material from other sources is very welcome.
Their Web Page
The site and group are very focussed on German sources. They do study Le Jeu de La Hache but none of the Italian school. Many useful links.
Schielhau: another group studying German sources.
The Selohaar Fechtschule. Concentrates on the Liechtenauer tradition of German combat manuals.
Wiktenauer. A very large collection of Historical European Martial Arts resources.
Translations and Interpretations:
The Medieval Art of Swordsmanship: A Facsimile & Translation of Europe's Oldest Personal Combat Treatise, Royal Armouries MS I.33 by Jeffrey Forgeng ca. 1300
Codex Wallerstein: A Medieval Fighting Book from the Fifteenth Century on the Longsword, Falchion, Dagger, and Wrestling by Grzegorz Zabinski with Bartlomiej Walczak Reviewed here. Compilation: oldest portion first third of the 15th c., rest ca. 1470
The Gladiatoria Fechtbuch by Hugh Knight Reviewed here. 1430s-1440s
"Ringeck" (Actually a compilation that ascribes some material to Ringeck,mentioned in the third person, and includes other material from unidentified sources) Plausibly from the 1440s, but could be as late as 1470 and perhaps as early as 1390.
Secrets of German Medieval Swordsmanship: Sigmund Ringeck's Commentaries on Liechtenauer Translated and interpreted by Christian Henry Tobler* Reviewed here. Available from Freelance Academy Press
Sigmund Ringeck's Knightly Art of the Longsword .
By David Lindholm and Peter Svard Reviewed here
The Ambraser Codex by Master Hans Talhoffer By Hugh Knight (commentary and translation) (Talhoffer 1449)
Medieval Combat: A Fifteenth-Century Illustrated Manual of Swordfighting and Close-Quarter Combat translated and edited by Mark Rector (Talhoffer 1467) Reviewed here
Paulus Kal's In Service of the Duke by Christian Tobler Available from Freelance Academy Press. ca. 1470
In Saint George's Name: An Anthology of Medieval German Fighting Arts by Christian Henry Tobler Reviewed here. (1452-1495)
Master Peter Falkner's Art of Knightly Defense Reviewed here ca. 1495
The Art of Combat: A German Martial Arts Treatise of 1570 by Joachim Meyer, tr. Jeffrey Forgeng. Reviewed here.
General Interpretation of the German School:
Fighting with the German Longsword, by Christian Henry Tobler
Fencing With Spear and Sword: Medieval Armored Combat
Grappling and Dagger Combat in Armor
The Play of the Axe: Medieval Pollaxe Combat
Introduction to Liechtenauer's Longsword
The Last Resort: Unarmored Grappling and Dagger Combat
Medieval Sword & Buckler Combat
The Knightly Art of the Longsword
Die Schlachtschule Fechtbuch
All by Hugh Knight on Lulu
Fiore dei Liberi 1409 Wrestling and Dagger by Colin Richards
Fiore de' Liberi's Fior di Battaglia By Tom Leoni
Fiore dei Liberi’s Armizare by Robert Charrett. Reviewed here and here.
Arte Gladitoria Dimicandi: 15th Century Swordsmanship of Master Fillipo Vadi translated by Luca Porzio & Gregory Mele* Reviewed here 1482-1487 Available from Guilt Free Books
The Complete Renaissance Swordsman : Antonio Manciolino’s Opera Nova (1531) tr. Tom Leoni
Fighting with a round shield strapped to the arm, as taught by the Bolognese School. First half of the 1500s.
Opera Nova by Achille Marozzo. Partial translation here As Arte dell’Armi (1536 ) and Opera Nova (1540)
Di Grassi his true Arte of Defence Also partially transcribed here. 1570, English translation 1594
Le Jeu de la Hache
MS 39564 Just because it's in English doesn't mean you'll be able to understand it. This is written in very specialized technical language, and we no longer have the glossary. 15th c.
Man yt Wol (Harleian MS 3542) Ditto. 15th c.
Paradoxes of Defense (1599) and Brief Instructions Upon My Paradoxes of Defense (after 1595) by George Silver
The Art of Riding on Every Saddle: Livro da Ensinança de Bem Cavalgar Toda Sela by Dom Duarte tr. António Franco Preto. Reviewed here, but note that the review is of the first edition. The second, which I have not seen, is longer and contains new content, and changes to the title, as well as what I know of the history of the first edition, suggest that the text may have been significantly revised. It is now published through CreateSpace rather than Chivalry Bookshelf.
Jousting in Medieval and Renaissance Iberia by Noel Fallows. Reviewed here.
Anthology: Various Schools
In the Service of Mars: Proceedings from the Western Martial Arts Workshop 1999–2009, Volume I
*Published by Chivalry Bookshelf. Please read this important information about Chivalry Bookshelf
Posts on this blog on recreating medieval combat. and on armor vs. weapons.
Armizare & Co.