I am an Irish citizen, resident in the UK & looking to fly back to Ireland without my passport (currently submitted for a driving licence application).
Wikipedia lists a number of documents as valid ID for travel to Ireland within the Common Travel Area, such as a work photo ID or bus pass, (though I unfortunately don't have these).
It also mentions "National ID card/Government-issued photo ID cards". I do have an EEA1 residence cert — but I presume this wouldn't count as a National ID (which I think means the credit-card style ID carried in Spain, Germany, etc.)
Would it be considered a Government-issued photo ID card though? It's a blue, cardboard document rather than a plastic ID card: