Today is the feast of St Patrick, the Apostle and patron of Ireland.
It is worth noting the initiative he represents on behalf of the Church in late- and post- Roman Britain to evangelise the adjacent island, and its success - this was a mission that produced no martyrs from any who resisted conversion. This is in contrast to the reaction of the British Church and its leaders to the Germanic invaders, who having alienated the Britons were not evangelised by them at all, but were rather, presumably, literally left to go to Hell. Converting the Angles and Saxons was to be left to the Roman mission and that from Irish roots at Iona after 597.
Anyone looking for a good introduction to the life of St Patrick and to his world view will not go wrong if they look at Thomas O'Loughlin's CTS pamphlet in the Great Saints Series. Simply entitled Patrick it provides in a relatively few pages an insightful understanding of St Patrick, drawing upon his two surviving texts, the Confession and the Letter to Corocticus.
There are introductory online accounts of the two cathedrals dedicated to St Patrick at Armagh at St Patrick's Cathedral, Armagh (Church of Ireland) and at St Patrick's Cathedral, Armagh (Roman Catholic).There is a more detailed history, with pictures and a series of links, of the Church of Ireland cathedral here.
There is a good illustrated online account of St Patrick's Cathedral in Dublin, the largest medieval church in Ireland at St Patrick's Cathedral, Dublin.