The UCD Maps and GIS Librarian has also very helpfully included a presentation on "Free websites sources for historical maps of Ireland" where she gives excellent guidance and practical advice on how to make the most of using these valuable resources.
Maps and clues in the geographical information associated with our ancestors are such a great resource for Irish research that I've made them the subject of a talk that I give called "Irish Research - Getting Your Bearings". If you would like me to entertain your local family history group with this subject, click on the link above to go to my Kindred Ancestry website and get in touch via my Contact Form.