I saw a great program on the Celts a few weeks back that I have been meaning to mention on this board. I believe it might have been on PBS - not sure if anyone caught it.
It basically examined the Celtic Pagen religion of pre-christian Ireland, Scotland, Wales, Britian. Alot of our traditions today are based on these Celtic Pagen rituals - like halloween.
What historians find extremely interesting is that all of the british isles where converted to Christianity without any bloodshed or terrible wars that have always accompanies these transfers in religion.
The therory, and it seems to have been proved by the makers of this film, is that alot of the Catholic rituals in church have Celtic roots. So in essence, when Christianity came to the isles, it was more of a conversion of the two religions with Christianity coming out on top. That is why alot of these Celtic traditions continue in present day.
Well, if you happen to grab a repeat of the show, I would highly recommend it. I believe it was based in Ireland and examined alot of the traditions that still presists in Ireland that have pre-christian roots.