Beltane: May 1 - Beltane had a variety of other names, including Beltine, Beltain, Beal-tine, Bel-tien, Beltein, and Beltan. This word means "bright fire." Beltane was celebrated to commemorate the beginning of Summer. People would begin to come out more regularly and hold feasts and fairs around this date. The cattle were also released into the pasture, the freezing winter over. Games were played in order to determine future marriage partners. Many marriages were also held on this holiday. It was considered a day of life and fertility, celebrated in honour of Beli and his counterparts.
Eisteddfod - This is of much lesser importance than the four above fire festivals. This festival was an annual bardic music and poetry competition. This still exists today, being held in North and South Wales alternatively. The rules state that no other language that Welsh is to be spoken on stage.
Imbolc: February 2 - Literally translated, Imbolc mean "in the belly." This festival represents the beginning of Spring. It was associated with the goddess Brigid. Imbolc is also called the Return of Light. Most rituals were celebrated in the home on this day. Some divination rituals were done, though, in an effort to determine when Spring would begin. We may have gotten the modern Groundhog Day from this ritual. Imbolc was also called Eumelc, which means "the first milking."
Lughnasadh: August 1 - Lughnasadh means the "commemoration of Lugh" or the "feast of Lugh." Lughnasadh was a fire festival of high importance. It lasted for two weeks before and two weeks after the actual festival day. It appears that this was in connection with the harvest, in order to give thanks for it. Also known as "Lammas," This festival was characterized by athletic competitions, in honor of the athletic feats of Lugh.