Ireland by Bus Eireann
A lot of people don’t like travelling by bus. Unfortunately, unless you’ve hired a car or are hitchhiking, you will probably find yourself on a bus sometime during your time here. Taking the train is great, but you’ll probably find either the price of tickets, limited destinations or sparse departure times don’t suit to get you everywhere you want to go, when you want to go there.
The good news is that most of the busses are brand new and their service areas cover the entire country. Their website is a good one, giving rates and times for service anywhere in Ireland. Make sure you produce some student ID if you have such a thing, as the student rates are quite good. There are specials happening on and off, year-round but, in general, a daytrip from Dublin to Galway (probably the most-travelled route for tourists) is less than €20.
The busses themselves are fairly comfortable, though sleeping on them takes a certain amount of immunity to noise and your limited room. Personally, I can fall asleep anywhere and have managed to sleep through more than a few bus trips; all I need is a window seat and something to use as a pillow against the glass.
Really, for the price and convenience, you can’t really beat Bus Eireann for getting around Ireland.