Celtic Myth and Legends of the Celts

Irish Legend
Feature on the Ulster Cycle.

Bulfinch's Mythology - The Age of Fable
Discusses a possible link between the main god of the Druids and Baal, and describes the Celts' ritual practices based largely on Caesar's writing.

The Celtic Druids
Britannia Internet Magazine's article by John Mitchell. Claims Stonehenge was built by Celtic druids in 2000 B.C. Mabinogion
The Mabinogion is a story that was not written down until the mid-13th Century.