The Guinness and Jameson tours are compulsory.
The museum @ Collins Barracks is pretty cool.
Blarney Castle is worth checking out (I'd recommend NOT kissing the stone).
Kilmainham Gaol is a must ("ki-MANE-um") The history/stories there are incredible.
Definitely see the Cliffs.
Dingle is great.
Clontarf Castle Hotel is pretty decent digs in Dublin (they were hosting some fashion/runway show with supermodels everywhere when I was there. Very nice.
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If you haven't secured a rental yet, Avis has relatively cheap Audis at the airport. Might have to reserve one in advance though.
Have fun.
