My sister was in Sligo recently and had a great weekend. She went surfing which is fun even if you're not very sporty! The town has some good restuarants and pubs, there are nice beaches and I htink there is a nice cliff walk. Other than that I can't help I'm afraid!
Hawkswell Theatre
Rosses Point beach and marina
Restaurants in Rosses Point. I rec. the Waterfront and Austies and the Moorings
Golf at Rosses Point and Strandhill
Omniplex cinema
Shopping Centre in Quayside
Yeats's grave at Drumcliffe
Glencar Waterfall nearby (yes - that's in Leitrim)
Pubs in town - Hargadons in O'Connell St. for one.
Surfing of course at Strandhill
Horse riding