On the 5th July each year the Isle of Man holds a public holiday for Tynwald Day. This is the one time each year when recent laws of the island must be promulgated - or read to the atendees - in both English and Manx Gaelic in order for them to continue to have effect.
It was rather disappointing googling for Tynwald Day to find that the Isle of Man Government haven't updated their own page about the day since the Queen attended in 2003. As our only national day, I would have thought that it would be really important to have an up to date information page about it on their website.
Update: It is listed in the tourism events calendar, but that's about it, and very little detail is given.