IrishSlang.info was created by Barry Flood, a student of Interactive Multimedia Design at the University of Ulster. You can see an interview with him below.
The site is well designed and there are some amusing video clips. It's a pity not all of the words and expressions have examples of usage as well as definitions. There's a spelling mistake in the logo too—it should be "horse's mouth" (if you hear something "straight from the horse's mouth", you hear it from someone who definitely knows it is true).