A valuable finding aid is Smith’s Inventory of Genealogical Sources: Ireland. It is an in-house inventory of sources at the Family History Library (FHL). They are usually referred to as Smith’s Inventory.
The FHL staff and volunteers compiled this inventory using only the resources in their British Isles collections, under the direction of Frank Smith. Unlike the famous Periodical Source Index (PERSI), which only inventories articles from periodicals, Smith’s Inventory adds these to sources hidden in books and the microfilm. The books are more self-explanatory, unlike the microfilm. Many microfilmed manuscript collections do not have page numbers. Smith’s Inventory mentions them, and then you have to backtrack in order to find the reference. This is not easy, but it’s usually the nature of Irish collections.
Smith’s Inventory is most helpful in accessing estate papers, freeholders’ lists, genealogies and tombstone inscriptions. While there are many subject categories, these are the ones I tend to use the most. Now be aware this is a dated source with the inventory published in 1994. Even at this, the value of bringing these hidden resources into the light cannot be underestimated.
Smith’s Inventoryis on microfiche. For Ireland the microfiche are as follows, all part of FHL #6110527: Irish General (Fiche #1-#3); Irish General-Antrim (Fiche #4); Antrim-Armagh (Fiche #5); Armagh-Cavan (Fiche #6); Cavan-Cork (Fiche #7); Donegal-Down (Fiche #8); Dublin (Fiche #9); Dublin-Galway (Fiche #10); Galway-Kildare (Fiche #11); Kilkenny-Leix (Fiche #12); Limerick-Londonderry (Fiche #13); Londonderry-Mayo (Fiche #14); Meath-Offaly (Fiche #15); Offaly-Tipperary (Fiche #16); Tipperary-Westmeath (Fiche #17); Westmeath-Wicklow (Fiche #18).
If you are accustomed to using the FHL microfilm, then this is a must to make sure you haven’t missed some of the more obscure and hidden sources.