I've been in Image Gym in Swords, highly recommended. Small basic gym with primative showers, but great staff who really know their stuff. Also, one of the few remaining squat racks and power cages in Dublin.
http://www.imagegym.com/
I've been checking out Northwood on Santry Avenue, same sort of facilities as Jackie Skelly, but much cheaper.
Morton Stadium, on the old Airport Road, also has a gym, 135 euro for six months, basic facilities but good equipement. Only trouble (for me) is it opens noon to 9pm. I like working out in the morning. It's also got squat rack and power cage.
I've checked out Total Fitness at Clare Hall. I thought the equipement was badly maintained, and the staff weren't helpful.
DCU gym has a pool, but no free weight apart from a handful of small dumbells. No barbells, never mind a squat rack.
Alssa seems light on free weights as well, and I'm sorry, I know it's silly, but the smell of curry puts me off.