Saxons and Vikings is a set of four page simple rules for Dark Ages battles
Here’s a short photo tutorial on making a dark ages livestock corral, which is perfect for your SAGA games.
Kings of War is a great free fantasy rules set from Mantic Games. Here’s a variant for the Viking Age
Ravenfeast is a set of free wargames rules for skirmishes in the Norse sagas.
The Command Tent has a nice post on how to scratch build a viking A frame house. I’m going to build a couple of these for my Viking/Saxon/Norman games.