At the moment, the largest party by a country mile is Fianna Fáil (FF), who are centrists, they are just short of a majority so they are in coalition with the Progressive Democrats (PDs), who are fairly right wing. Our Taoiseach (PM), Bertie Ahern is the leader of FF, a man of the people, but also been called the 'slyest and the most cunning of them' all by a former Taoiseach, Charlie Haughey, who was no clean slate himself. The leader of the PDs, Michael McDowell, is a bit of a firebrand who doesn't know when to shut up, but probably there are very few people who don think he is not a Justice Minister. FF are the traditional largest party, traditionally popular with the masses, despite acting like gangsters and serving themselves, but to be fair, as they are almost always in power, so they most do something right.
The most likely alternative government is a Fine Gael/Labour/Green Party coalition. Fine Gael (FG) are lead by Edna Kenny, and are also centrists, Labour, lead by Pat Rabbitte and are left of centre and the Greens, led by Trevor Sargent (only Protestant in the Dáil (parliament)), are, well green and like bicycles. Fine Gael are the traditional second party of the country, traditionally popular with the larger farmers and such.
The other party, the black sheep of Leinster House, are Sinn Féin, who are expected to win some more seats in the more Republican areas, but none of the other parties will have anything to do with them, even if it was a hung Dáil.
Despite our economic miracle, our health services and education are still crap, lack of doctors, nurses, teachers, hospital, schools, etc., and with the expected fatigue of the same government for two terms already, the FG/Labour/Green coalition is a possibility, but Bertie has a canny knack of plucking victory from the jaws of defeat.
Should be noted that in Ireland, we use the pretty good single transferable vote system, a form of proportional representation, wiki piece on it
I think that is a decent summary, if/when I vote (depends on if can as I won't be in Ireland), my first vote would be for the local independent candidate, as I know him, lives down the road and has fairly sensible ideas. Next votes would be probably for Labour, then Green, then FG, basically we need a change of government, two full terms, 10 years, is enough for any government.