The Norn are gigantic warrior people from the frozen Northern Shiverpeaks. They value individual prowess in battle above all else, and such have little to speak of when it comes to organised society; each Norn stands relatively alone.
In terms of physical appearance, they are obviously inspired by the Nordic warriors such as the Vikings and the Normans. The men are typically broad chested, muscular and often sport manly-man beards. The women are Amazonian in stature and are equally skilled in battle. The Norn worship the spirits of the wild - choosing to focus on the strongest, bravest and wisest animals in the Shiverpeaks - as such the Norn can transform themselves into the shape of their chosen totem - either the Raven, Wolf, Snow Leopard or Bear at will to increase their ferocity in battle (as far as I'm aware; in game, a Norn will be able to transform into any of these forms and will not be restricted - but don't quote me on that!).
Since the end of Guild Wars 1, the Norn have been ousted out of their homeland in the mountains and forced south by the arrival of the Elder Dragon Jormag. The dragon slept beneath Drakkar Lake for centuries (and if you visit there in GW1 you can see him under the ice - kinda creepy now you know who he is)**. When Jormag emerged from his slumber he corrupted the surrounding landscape, bringing Dragonspawn of ice and snow and forcing many Norn to abandon their homes in favour of the safety of the Southern Shiverpeaks and sometimes even further south.
During the events of GW:Eye of the North we see how Jora's brother Sanvir was corrupted by Jormag's power and turned into a half-man-half bear (half-pig) monstrosity. Eventually, Jora is forced to kill her brother to put an end to his suffering, but in the years between Sanvir's death and the events of GW2 a cult has arisen which worships the Dragon just as poor Sanvir did and is as such just as corrupted as Sanvir himself. The Son's of Sanvir threaten the Norn as much as the dragonspawn - I'm hoping we'll learn a lot more about them as Norn week progresses.
The Norn have an uneasy alliance with the Charr - through mutual respect of their militaristic abilities. Not much else is known about their allegiances, its assumed they are on reasonable terms with the other races, although I don't imagine they appreciate the arrogance of the Asura, or have much patience for the naivety of the Sylvari.
I commented on the KTR post a while back stating that it might be difficult to integrate Norn and other races' cultures in places such as Cantha and Elona when there seems to be little lore-base to do so. With this in mind, it will be interesting to see if ANet sow any of these seeds for the future in the coming week.
ps. I am aware that villainously isn't a word.
** 19/04/11 - it's come to my attention that the creature under Jakkar Lake isn't Jormag - it's one of his champions. Christ, that thing is huge enough, and he's just a peon!