The Norse God Odin has two ravens - one called Huginn and the other Muginn, they were kind if like scouting out the world for him brining him back tidbits of gossip and what not. ( i.e. was Freya's hair REALLY blonde?!)
They would leave at sunrise and return at dusk and perch on his shoulder whilst imparting their juicy stuff.
Translated into English Huginn means 'thought' and Munin 'memory'. An old Norse text contains the following verse:
'The whole world wide, every day,
fly Hugin and Munin;
I worry lest Hugin should fall in flight,
yet more I fear for Munin.'
One of Odin's titles was 'God of the Ravens' and his daughters the Valkyres were often thought to assume the form of the Raven.
Ravens are also imbuded with powers of omen and foresight, and a sa guide for the dead...hence the association with Valkyres I suppose....
Sorry for the overload.