Here is an interesting article about Vikings from Medieval News:
"A new theory about what drove the Vikings to raid Western Europe in the late eight and ninth centuries has been published. It suggests that the Vikings in Denmark were reacting to a threat from the Carolingian ruler Charlemagne, who was seeking to destroy their society and impose Christianity on them.
The theory was put forward by Robert Ferguson in an article for the December 2009 issue of BBC History Magazine. His book, The Hammer and the Cross: A New History of the Vikings, was also published in November." ...(Cont.)...
Here is a podcast interview with Robert Ferguson from BBC History Magazine.