The systems we are currently focused on are Liechtenauer's Kunst des fechtens (arts of fighting), and Highland Broadsword (mostly according to Page).
Liechtenauer's Kunst des fechtens
More than two dozen manuals were written on Liechtenauer's school of swordsmanship from the 14th to the 16th centuries, making it the most enduring system of the middle ages. Although his teachings focus on the use of the longsword (a sword normally wielded in two hands, but light enough for one),the principles of Liechtenauer's art can be used with most other weaponry common in 15th century Germany, including dagger, arming sword, spear and unarmed combat.
A collection of some of the available German manuals can be found here.
Highland Broadsword
In 1746, when the last Highland rebellion had only just been defeated, an English soldier, Thomas Page, set about recording the style of fighting then in use by the Scottish Highlanders. His manual is a remarkably clear set of instructions for the basket-hilted broad sword, and includes a section on sword and targe.
Page's The Use of the Broad Sword can be found here.
There are many other manuals detailing diverse WMA systems. A few of the other styles we have studied in the past include:
MS I.33
Written around the turn of the 13th and 14th centuries, the anonymous 'Tower MS I.33' is the oldest known European fighting manual. It details a series of lessons in sword and buckler (a small shield) given by a priest to his student.
A translation of the I.33 manuscript can be found here.
George Silver's "True Fight"
The rapier dueling craze of the Renaissance prompted Englishman George Silver to record the principles of the vanishing "true fight". This was a more medieval style of fighting, focusing on the basket-hilted "short" sword but including many other weapons, such as dagger and staff.
Silver's Paradoxes of Defence can be found here. This manual has little technical detail and is mostly a rant against rapier fencing, but Brief Instructions Upon My Paradoxes of Defence can be found here.
Others
"Western Martial Arts" is a very broad topic, covering everything from the historic sword systems we study, through to rapier, pugilism and even modern systems such as boxing. Probably the best place to start is the manuscripts page of the Resources for Historic European Martial Arts website.