There are lots of interesting festivals and fairs throughout Ireland, especially in the summer months.
Puck Fair: is a traditional annual fair, held in Killorglin, Co. Kerry for the past 300+ years. A wild adult male-goat (puck) is crowned 'King of the Fair' for 3 days and then released back into the mountains.
Trim Hay Making Festival: is held in the heritage town of Trim, Co Meath each year in June (this year 14,15,16th June) It features horse and vintage-tractor mowers; animal parade; donkey-derby; arts and crafts; wren-boys and much more. A celebration of cultural heritage and traditions plus a host of other events with fun, music and dancing. See the official site: http://www.trimhaymakingfestival.com
Spancilhill Horse Fair: Each year on the 23rd of June (Midsummer Eve or St. John's Eve) the famous Spancilhill Horse Fair is held on the nearby Fair Green. The first charter for this historic fair was granted by King Charles over 300 years ago and in the past, the fair lasted for a week or more. At one time, Spancilhill was said to be Ireland's largest fair with buyers from Britain, Russia, Prussia, and France competing to purchase the best stock for their Imperial armies. In recent times it has evolved into a one day show and fair where the leading horses and donkeys in the country are presented. It attracts up to 5,000 horses and more than twice as many visitors each year. References: http://www.spancilhillfair.com/html/history.html http://en.wikipedia.org/wiki/Spancill_Hill
Clarinbridge Fair: a traditional fair held each year in Clarinbridge, a small village at the eastern end of Galway-Bay, in early September, to mark the start of the Clarinbridge Oyster Festival.
Dunderry Fair: is an annual event held in May in the village of Dunderry, Co. Meath. The proceedings are donated to charity. http://www.dunderryfair.ie/