Hi Mark, firstly the weather isnt so great so bring a rain jacket. The center of Dublin is relatively small so you can wander arround on foot - my top 10 would be the following:
1) Nightlife on Camden St - Whelans (for live gigs), the Village and Solas (irish for light)
2)Eats - head to Cafe Bar Deli on Grafton St in the famous old Bewleys Cafe for cheap and cheerful grub
3)Shopping - Grafton St and Henry St are the 2 main shopping Streets.
4)Georges St and the Powerscourt Centre - nice to look arround, bit more funky. The Market Bar and Hogans are 2 great pubs round here.
5)Culture - make sure to check out the Molly Malone Statue at the end of Grafton St.
6)Walk thru the grounds of Trinity College - esp worth a visit if the weather improves. You can see the book of kells here if you wish. I think its a bit dissappointing.;-)
7)Temple Bar - ah you have to check it out even tho its quite touristy - visit on a sat morning - go to Meeting House Sq for the open market and check out the gallery of photography.
8) The Italian Quarter - look out for the millenium bridge and go accross it to Dublins italian quarter (near the jervis centre)
9) Merrion Square and the National Art Gallery - good to visit on a sunday morning when local artists sell their wares all arround this little park.
10) Escape from Dublin for the day! The Wild Wicklow tour is quite good or get a DART (light rail train) to Howth or Dun laoghaire - both are about 20 mins away by train - Howth is probably nicer.
I forgot the Guiness Storehouse - this is worth a visit. You get a great view of Dublin from the top of this, and the guiness is good too, enjoy!