I was in Dublin a while ago but we loved the zoo. Also, we did an open top bus tour which was a good way to get around as as had no car etc, so we used that as a combined sightseeing/transport. St Stephens green (I think that is the name) is nice on a nice day and it is decent for shopping too. Temple bar is nice for a wander but really busy, we went during the day (before lunch) and had a nice breakfast in some studenty place - it was a while ago so can't remember the name but we enjoyed it anyway! Oh, and the Guinness factory.