As far as longsword fencing goes. The most commonly practiced Is the german style and the itialian style, I belive there are were some english masters who left books too(sliver to name one) Though some would argue(and I agree) that all of those "styles" are one masters take on one art. Afterall italy and germany were both the holy roman empire at the time when longsword was used the most. The major differance between italian and german is that the germans tend to stay at the sword, or in a bind more. That is useing techniques while the swords are touching. While italians tend to be much more Parry riposte oriented. But each style has elements of the other. I myself study the techniques described by Johannes Liechtenauer and his line of students which is the primary source for all of the "german" techniques. Books that i recomend on the subject can be found here: http://www.revival.us/index.asp?PageAction=VIEWCATS&Category=216
They have the best books on both itialian and german styles as well as other arts besides the longsword.
As a side note A long sword is generally described as a sword that has a hilt anywhere from 7 inches to 11 inches and a blades rangeing from 34 inches to upwards of 40 inches. In the historical treatises the germans are illustrated useing swords on the longer end of the spectrum, while italians and english seem to prefer the shorter swords. which makes sense because a shorter lighter sword crosses and uncrosses quicker lending itself to the parry and riposte style better. while the longer swords are better to work from the bind or crossed swords.
To clarify a bit; working from the bind or Am Schwert(at the sword) consisted of moveing the sword to various postitions trying to get your point online for the thrust, or to cut them from their blade, or slice them from thier blade. And those types of techniques are called winding, which are almost exclusive to the german styles. Now I know it might seem stupid to say at the sword instead of disengaging and finding another oppening(which the germans did do if neccisary) but look at it this way: Its like the old conflict between grappler and striker. even if your a striker(parry and riposte) you still need to know how to effectivly counter a grappler(winden am schwert). Well enough rambling on my part. buy the books or go to www.swordforum.com
to learn more from more knowledgable people.