While on the subject of Online Irish Language courses, here is a link to a BBC Irish language learning site, that specifically teaches Ulster Irish. While it is not exactly comprehensive, and certainly will not make you fluent, it does give you a good working knowledge of the basics of the language (and you learn a little folklore along the way too sometimes). It is also free.
http://www.bbc.co.uk/northernireland/ir ... son1.shtml