For the culture and history of Ireland I don't think there's any way around just doing good old fashioned research on your part. Libraries, google, etc, whatever your method is. For the folklore, you may have an easier time as there's less emphasis on getting the facts exactly accurate. If you have an iphone there are several apps that are just mini databases of mythological creatures. If you search the app store for "myth creatures" I'm sure you'll find several you can use. I don't know about you but if I have to do research, I prefere to enjoy and be entertained by the process and who doesn't enjoy watching TV right? Here where my next suggestion comes in. There is a TV show that's made in Canada called "Lost Girl". I don't know how it's broadcasted internationally but in the United States it airs on the SyFy network. In a nutshell the show is about a woman named Bo who discovers she's a Succubus, which she also finds out is just one of many species of Fae. This show is crammed full of mythologic creature and culture references (even a few flashbacks to times of the ancient celts). Granted some of the creatures in the show are not specifically Irish, (i.e. Fury (Greek), Siren (Greek), Minotaur (Greek), Dwarf (Germanic), Golem (Jewish), Frost Giant (Nordic), Aswang (Filipino), etc.) but many of them are Irish (Daoine Sidhe, Kelpie, Banshee, Dullahan, Selkie, Leanan Sídhe, etc.). I'll admit, I'd seen many previews for this show and thought it was just some low budget "straight to DVD (if ever)" show, and sure the special effects may not be movie quality but the stories and myth more than make up for that. I'm hooked now. Give it a watch and see what you think. Good luck.