The Buntús Cainte series of books for learning Irish are an older set of books, but I like them very much. As a learner of Scottish Gaelic for 21 years and Irish for two years, I found the language in the initial lessons to be very similar to Scottish Gaelic. This ‘eased’ me into Irish, which I appreciated.
Well, now they seem to have an app! Check out buntuscainte.com and follow them on twitter @BuntusCainteApp.