The recent popularity of vikings and the interest in
ancient history in the
Nordic countries has led to a lot of
research on the subject in the last decades. A lot of what has been written about the vikings is now questioned and therefore it's hard to present any hard facts about them, but I'll try to summarize.
First of all: Not all people living in Scandinavia during this time (750-1050 A.D) were called vikings, and viking is not a nationality. In old norse texts the word "viking" is used to describe the activity of sailing out to plunder or trade. Being a "viking" was just a part-time job. Back home the vikings were Norse, Swedes, Geats, Danes or Icelanders, living their lives as farmers, fishermen, merchants and other peaceful occupations. The Webster etymology of the word is just one theory. Another one is that the word comes from the old norse verb "vikja" - to depart.
Then there's the "invading, burning, looting, and pillaging". Well, there were certainly some of that going on, both in between the "viking nations" themselves and in the rest of Europe. Crews from viking ships also hired themselves out as mercenaries. The activities of Danish vikings in England and Norse vikings on Ireland are well known, mostly violent stuff. What people tend to forget is that the vikings were also traders. Swedish vikings traveled east through the Baltic states, Russia and down the Dnepr to Belarus and Ukraine, where they founded Kiev as one of their major trading posts. They even got down to Turkey and got really exotic merchandise from the Turks. Some plundering probably occured on these trips as well, but the main purpose was trade.
If you want to read a contemporary description of the vikings I strongly recommend Egil's Saga. For a more modern and not terribly historically acccurate story, try the The Long Ships by Frans G. Bengtsson. Both these books are a lot more fun to read than you would expect, because one thing about the vikings is definitely true: They weren't boring!