This is an amazing site to visit, but note that

a) you need a bit of a head for heights, ie if you suffer from vertigo the climb up or more likely the walk down can be pretty scary

b) it's a summer-month thing, between May to September are the only possibilities and even then you need to be lucky with the weather to get a day when the boats can actually land on the island.

I accessed it via the village of Portmagee which is just off the Ring Of Kerry - like others on this site I heard great things about Des Lavelle (who is a local historian and who is based there) and therefore pre-booked with him, by phone - however when we showed up the day before they claimed not to have heard of us and to be fully booked out, wasn't too impressed with them therefore.

However there are plenty of operators in the village (do book in advance in the high season though) and the local bar/hotel/restaurant The Moorings is simply great for a pint, some traditional music and a plate of fish and chips