In no particular order:

(1) Cliffs of Moher
(2) Newgrange
(3) Book of Kells
(4) Rock of Cashel

Roy stole my answer! These are the four I would have chosen, too.

Dun Aenghus
Giant's Causeway
Newgrange
Rock of Cashel

Glendalough, Newgrange, Ring of Kerry, Dingle Peninsula/Cliffs of Moher (sneaking in one more - Antrim Coast)

Dingle, Giants Causeway, Newgrange, Antrim Coast.

Cliffs of Moher, Newgrange, Giants Causeway, Dingle.
A night in "An Droichead Beag" pub in Dingle will be memorable although in the morning they maybe somewhat blurred!

1)Dingle (everything in/around Dingle is amazing)
2)Slieve League Cliffs in County Donegal - I would argue they are more impressive than the Cliffs of Moher (certainly higher) and much less touristy. Although if you can't get to Donegal then I would substitute for the Cliffs of Moher.
3)Walls of Derry/Bogside
4)Giants Causeway

1. About any country pub with a big turf fire on a rainy Saturday afternoon.

thanks to all the replies and hope to hear more !!! I am really enjoying the answers !!! it sounds like the pubs are a definate must do ....

1) Great Blasket Island
2) Dingle Peninsula
3) Aran Islands
4) Book of Kells and Trinity Library

Antrim area ,Dingle Peninsula,Aran Islands,Trim Castle

dingle...kinsale...rock of cashel...wicklow mountains...cliffs of moher/the burren

Newgrange and (I know I'll get beat up for this) Blarney Castle.

The real treasure in Ireland, however, is it's people. Visiting a pub in any smaller town is like visiting relatives that you like a lot but don't see nearly often enough.

I also think a traditional session in a pub is worth the cost of the trip.

I've got to cast a vote for the 1916 walking tour in Dublin. One of the best things from our trip this summer.

Book of Kells and the Library, Newgrange, Glendalough via the Sally Gap and the Giant's Causeway. Pubs are a GIVEN. Especially those in the smaller communities you'll be driving through. Best way to meet the lovely Irish people.

1) Any Pub in Dublin (and anytime of the day)

2) The Aran Islands & Dun Aengus (can I count this as 1? I'm going to because they're connected - literally)

3) Connemara

4) Ring of Kerry (yes I know it's crowded, but it's a beautiful drive)

1) Kenmare

2) West Mayo

3) Any spot drinking a Guiness

4) Wandering the ancient streets and shops of Galway.

I found the Cliffs of Moher disappointing. VERY crowded.

But it is beatiful and worth seeing if you're there. Just get ready for a mob.

I think Brad's right! The best thing about Ireland are its people. Try Portumna and the Oak Lodge B&B to see what I mean.

Here are my choices...not in any particular order.

Northern Ireland

Republic of Ireland

Any pub that is open

A "pint"

Everything else is included with the above.

Dingle, Trim Castle, Giants Causeway,Dunluce Castle,Aran Islands-it is all great ! Going back next month for my fourth trip ! PS-ignore the weather-it is a given-it WILL rain !