Irish dialects have always varied widely from one county to another. With the advent of radio, television, easy travel, and other factors, the individual dialects are disappearing. The The Doegen Records Web Project is an archive of Irish dialect sound recordings made from 1928 to 1931 containing folktales, songs and other material recited by native Irish speakers from 17 counties. Crucially, it includes examples of dialects that are now extinct.
You can learn how your Irish ancestors spoke at the Doegen Records Web Project at http://www.doegen.ie/.
My thanks to newsletter reader Michael Lee Stills for telling me about this valuable online archive.