Druids

A druid was a member of the priestly and learned class in the ancient Celtic societies of Western Europe, Britain and Ireland. They were suppressed by the Roman government and disappeared from the written record by the second century CE. Druids combined the duties of priest, judge, scholar, and teacher.[1] Little contemporary evidence for them exists, and thus little can be said of them with assurance, but they continued to feature prominently in later Irish myth and literature.[2]
The earliest record of the name druidae (Δρυΐδαι) is reported from a lost work of the Greek doxographer Sotion of Alexandria (early second century BCE), who was cited by Diogenes Laertius in the third century CE.[3]
The Celtic communities that Druids served were polytheistic. They also show signs of animism, in their reverence for various aspects of the natural world, such as the land, sea and sky,[4] and their veneration of other aspects of nature, such as sacred trees and groves (the oak and hazel were particularly revered), tops of hills, streams, lakes and plants such as the mistletoe.[5] Fire was regarded as a symbol of several divinities and was associated with cleansing. Purported ritual killing and human sacrifice were aspects of druidic culture that shocked classical writers.[6]
Modern attempts at reconstructing, reinventing or reimagining the practices of the druids are called Neo-druidism.
http://en.wikipedia.org/wiki/Druids

Nature Centered Spirituality
Many Druids are animists, which is sometimes mischaracterized by modern commentators as "nature worship." Like the Native Americans, most Druids see all aspects of nature as imbued with spirit, a soul if you will, whether or not they interpret that literally or metaphorically. Like the deities of the Celts, the animals and plants are seen as members of a Tuatha, or tribe. The spirits of nature are seen as relatives of an extended family and are therefore honored as kin. The whole of nature along with the other spirits of the unseen realm are seen as a large tribe of tribes, a familial way of describing the interconnectedness of the ecosystem that is the earth. The mother Goddess Danu gives her name to both the tribe of the deities, and the overall tribe of tribes, which in the Gaelic is the "Tuatha De Danaan," the tribe of Danu. The hierarchical concept of worship involving submission and obedience by us as lesser beings is not a concept compatible with Druidry, despite the frequent misunderstanding base on the Judeo-Christian hierarchical concept of worship.
http://en.wikipedia.org/wiki/Neo-druidism