The Dark Age Wargaming Blog has a nice (long) article (in multiple parts) on the historical Age of Arthur. Doing an historical Arthur skirmish game has been one of my longtime goals.
Dark Ages
Viking Flags
The Man Cave has a couple of printable Viking flags.
Free Viking Shield Decals
An Hour of Wolves and Shattered Shields has a selection of high resolution shield designs for Vikings. Either print them out on decal paper, or on regular paper and glue them to the model.
Villehardouin Free Board Game
Villehardouin is a free map-and-counter board game from the great designers at Perfect Captain. It’s a game about the Byzantine Reconquest of the Morea in southern Greece in the year 1263 AD.
Viking Painting Guide
Crusader Miniatures has a painting guide for Vikings.