Have to recommend the Abbey Hostel - situated just off O'Connell Street and a two minute walk from the Temple Bar area of the city. It's nothing fancy but it's very cheap (about £13-20 per night) and you can choose from double rooms with en-suite facilities; rooms for 4/6/8. We stayed in a room for four - there were two bunk beds and en-suite bathroom with the best power shower EVER! I would recommend that if there were only two people going and you couldn't get a double room - pay the extra for the other two beds so that you have the room to yourselves! Still cheap! It's ideal for a base for a weekend trip when you're only looking for somewhere to rest your weary head after a hard days sight seeing and Guinness drinking!