There's loads to see and do in Cork and the surrounding area. In Cork itself, you've got the old City Gaol, whic is worth a visit; St Finbarrs Cathedrals is gorgeous, and you can ring the bells of the Shandon church which is on a hill overlooking the city on the north bank of the river Lee.
Juts outside the city you've also got Blarney castle, the port of Cobh, and I thouroughly recommend Kinsale, site of a major battle during Elizabethan times, and home of two very good castles.
You can get more info at www.corkcity.ie/corkcity.htm