Everybody loves the Vikings. Or at least everybody does now. Back in the Middle Ages, it was an entirely different story.
There had been Germanic peoples settled in Scandinavia since the time of the Roman Empire. The Romans never tried to conquer them, but traded them with them for things like walrus tusks and amber. They scraped out a living farming the narrow fields along the fjords and fishing. In the eighth century, they developed the long ship, that could be either sailed or rowed, and decided it would make excellent sense to go raiding. ("Viking" is actually a verb.)
Raiders, usually led by an out-of-favor chief or deposed king, attacked villages and monasteries in western Europe, carrying away loot. The Vikings were terrifying fighters. Some monks had to flee repeatedly, because Europe's rivers made excellent transportation networks for the shallow long ships. A common prayer was, "Preserve us from the Vikings and their terrible dogs." Imagine Great Dane dogs that were fierce rather than friendly and a bit stupid.
The Vikings (who never wore horned helmets, contrary to Hagar the Horrible) also established some trading colonies in western Europe, realizing one could only raid an area once but could make a profit in trade every year. They also explored to the east, establishing what later became Russia and continuing all the way overland to Constantinople, where the Byzantine emperors hired these tall, powerful fighters as their so-called Varangian guard.
All during the ninth century Vikings attacked England, France, and what are now the Benelux countries. In England, King Alfred the Great fought back and eventually forced and bribed them to settle only in what was called the Danelaw region of northeastern England, where they gradually intermarried with the locals and adopted Christianity.
In France, King Charles "the Simple" granted them the region now known as Normandy in the early tenth century (it was named for the Norsemen). Again, they settled down, started speaking Old French, and became Christians--even if always very lively Christians.
Many Norsemen stayed in Scandinavia. They explored westward, settling in Iceland and Greenland, even briefly reaching the Canadian maritimes. Iceland was run by an elected assembly. Around the year 1000 they voted to convert to Christianity.
We still have a number of sagas and legends they wrote down once they became Christian, some of which, like the Saga of the Volsungs or the Poems of the Elder Edda, referred back to their pagan gods and myths. Most of the sagas, however, were tales of relatively ordinary Icelanders who ended up killing their relatives. All the sagas were written in Old Norse, which is extremely close to the language still spoken in Iceland (though they have added words for things like TVs and cars of course).
I have written my own epic saga, Voima, available as an ebook from Amazon, http://amzn.com/B004ZGI3Q8, as well as from other e-tailers. It combines elements of the sagas with elements of the Finnish Kalevala, which, both the Icelanders and the Finns will tell you, are very different. The Finns are an entirely different ethnic and linguistic group than the other Scandinavians, being close only to Hungarians. But from an Anglophone perspective, they both look like good traditions from which to borrow.
I've got dragons, long ships, pagan gods, and wars. It's my version of what Norse legends might be like if they were still being written.