If you want to do something that you'll really remember, walk to the top of Killiney Hill. Killiney is about 25 minutes down the DART rail from Dublin - from there, walk up Vico Road, admire all the beautiful mansions along Killiney Bay, and then walk the trail up Killiney Hill to the monument/park at the top. The view is absolutely breathtaking. The walk from the station to the top is about 25 minutes, the walk back down is about 20. You can see the Wicklow mountains, all of Dublin, the Bay, and Bray in the distance. When the winds are howling it feels great.

On the way back, I'd go to a pub or restaurant in Dun Laoghaire or Dalkey, both great towns to walk around.

In Dublin itself, the Jameson Distillery is always fun (ask to be a taster and you and 3 others will get 7 half-shots to taste ) and only 7 Euros. The Guinness Storehouse tour is very well put together but massively huge and if you want to go to every floor it would take forever. I looked around for about an hour then went to the top for my 'free' beer. Fantastic view of Dublin from there too but no chairs!

Most of the bars in the Temple Bar area are very touristy but they can still be fun - I like the music in the Oliver St. John Gogarty and they have tables toward the back left. A lot of the nicer quieter pubs are away from city center, I went to a couple nice ones in Rathmines but I forget where exactly.

If you're not staying near the river, take a stroll down it... as far as attractions, Trinity College is worth having a look at, and you can see the Book of Kells in the library if you want to, though I've never done that. Leo Burdock's has the best fish and chips in Dublin, if you call that an attraction .

If I think of anything else, I'll post... most of all, relax and enjoy yourself ^.