The Chief Herald is the authority on all heraldic matters relating to Irish families. The Office has also been known as the Genealogical Office since 1943 and is a part of the National Library of Ireland.
This Foundation in the USA is in some ways a cross between the White Lion Society and The Heraldry Society in the UK. This site tells you all about it.
This commercial site belonging to the publishers of "Burke's" has a wide selection of arms. Armigers may have theirs added upon paying the appropriate fee.