1. The Bureau of Military History
is essentially a massive collection of interviews with eyewitnesses and people who fought in the period 1913-1921. The search function is singularly useful. You can put in a surname, street name, town or even a keyword like "court" to see who presided over the local republican court. It has mentions of various safe houses and arms storage points.
Here are 12 interviews that I came across on the BMH website, and again the incredible Irish Folklore Commission in UCD was central to making these records. This batch of voice recordings includes Maud Gonne, Seán Mac Eoin, Áine Ceannt, Oscar Traynor, Kathleen Clarke and others:
The whole website is addictive: Bureau of Military History
I assume you're aware of the Dan Breen, Tom Barry and other interviews on YouTube? The Dan Breen one
(from about 2:05 on) I found to be especially moving.
2. Cnuasach Bhéaloideas Éireann/ The National Folklore Collection
Of course, if you want the mother of all oral histories, the Irish Folklore Commission in UCD, which was established by de Valera in 1935, is where you should head. It really is an exceptional repository of Irish oral history. Hugely underappreciated in Ireland today.
National Folklore Collection: Audio & Video Collection
The Audio & Video Collection features some 12,000 hours of audio recordings, including a large collection of early audio formats such as wax cylinders, acetate disks, wire-tape and magnetic-tape recordings. The interviews recorded cover many aspects of Irish folklore, folk music, ethnology and oral history, and were collected, for the most part, by professional fieldworkers. The recordings are in English and in Irish, with other languages, such as Breton, Manx and Scottish Gaelic, also represented.
This Collection continues to grow through active field recording and donations of audio and video recordings by members of the public.
The famous Doegen Records Web Project: Irish Dialect Sound Recordings 1928-31
is part of it. That website, too, is superb. You click on the county and then have a list of speakers and can listen to them while reading the transcript below it. Part of Doegen was published in recent years under the title Ulster Gaelic Voices
by Róise Ní Bhaoill, and it has two cds of the oral interviews. In Munster, the famous seanchaí Bab Feiritéar (1916-2005) in Dún Chaoin was similarly recorded, with the completed recording part of at least one published book, Coiglimis an Tine
Lastly, the GAA has been doing a massive oral history collection for the past ten years or so. Click on the county, for instance, the player and then listen to them: GAA: Oral History project