Depends what you are after. http://www.barnacles.ie/ is a great spot for a clean, cheap, friendly (lively) spot right in the thick of things. http://www.jurys.com/ has always served us well in Dublin and elsewhere in Ireland. A bit pricier (though still relatively affordable) and two well-placed sites in the centre of Dublin. http://www.hostelworld.com/ books both dorm-type and B&B accommodation in Dublin (and all around the world). Mrs Fuego is booked through them to stay at: http://www.charlesstewart.ie/ with her mates from tomorrow night until Monday. Hope this helps.
I have stayed at Comfort Inn Parnell Square. Nothing spectacular, but decent enough. Its not in centre of nightlife, about 10 minutes walk, but there are a few pubs on the way, and a pub in the hotel. Just at the top o'connell street if you know the area. http://www.comfortinnhoteldublin.com/
Ar lass stayed there recently on a hen do and said it was fine. I stayed at one close to the railway station that was decent but can't remember the name!