I am involved with several UK dark-age re-enactment societies, each of which excels in its own special way.
The Dark Ages Society is small, friendly and involves a great deal of fighting in small groups, feasting on wild boar, mead and so on, and quite a lot of genuine research into the history, crafts and way of life in Britain in the late 9th Century AD. Everyone in DAS develops a Viking or Anglo-Saxon persona: I am known as Ingibjorg and am a member of the Hólmbyggja.
Wychwood Warriors is the Oxford University Dark-Age Re-enactment Society, founded for and run by students to study and re-enact Anglo-Saxon culture. They sing all night and they never sleep, and the axe-pulling has to be seen to be believed.
The Vikings is a large national society which performs public displays of combat and living history, covering the entire period of the Dark Ages up until the Norman Conquest.
In 2005 I organised and participated in a display at the Woolwich Arsenal, London, to celebrate the voyage of the Norwegian longship 'Gaia'.
More information about the Wulwic Viking Invasion