Abair have a firefox plugin which will synthesize a word in Irish:

http://www.abair.tcd.ie/index.php?page=faq&lang=gle#firefox

http://www.abair.tcd.ie/index.php?page=faq&lang=eng#firefox

Or rather, it uses the search interface to invoke the website.

‘Tis worth the effort to join Abair.ie—ríomhchainteoir!
Eventually you’ll get to the screen where you select “Say it” and a dialog box will download in which you can enter your own written Irish sentences and/or written Irish from Irish language sites like BEO.ie and it will give you the spoken Irish!

Le meas.