What are the major Wiccan holidays....?

Answer 1

The eight Sabbats. The 13 esbats.

Answer 2

The Celtic pagan holidays each correspond to a stage in the life cycle.

Imbolc, Feb 2, first awakening of spring (birth)

Easter/Ostara, March 21 and Easter day, Spring in full blossom (bloom of youth)

Beltane, May 1, beginning of summer (thriving)

Midsummer, June 21, full summer (adulthood)

Lammas, Aug 2, first of autumn (first harvest)

Mabon, Sept 23, Autumn (full harvest/aging)

Samhain, Oct 31, first of winter (passage into death)

Yule, Dec 21, midwinter (hope of life/light in midst of death)

Answer 3

The eight sabbats:

http://paganwiccan.about.com/library/basics/blsabbats.htm

http://en.wikipedia.org/wiki/Wheel_of_the_year

and the thirteen esbats:

http://en.wikipedia.org/wiki/Esbat