1066: Year Of The Comet is a free print and play block game (you supply the blocks) about the Viking and Norman invasions of England. It looks terrific.
A Great Victory is a set of free wargames rules for miniature wargames set in the pregunpowder era.
Age of Arthur is a set of free wargames rules for Dark Ages Britain.
Here’s a scan of a classic Viking raid scenario from a twenty year old Practical Wargamer issue.
Dux Homunculorum has a tutorial on painting dark age figures.