One of my favourite cultural events of the year is Messiah on the Street. It's a choral performance of Handel's Messiah performed on Fishamble Street - fittingly so, given that that is the site of the original world premier of Messiah. So if you've time, turn up at 1 pm on Tuesday April 13th. Really, you should; if the weather is at all nice it is a lovely, happy crowd experience.
Temple Bar Cultural Trust have built a series of events around this main event.