"VeneziaNews" is a bilingual Italian/English publication which is the best guide available to the events, museums, music and dining in Venice every month. It seems to have disappeared from the net recently, but Agenda Venezia is a searchable website that appears to be powered by the magazine.
Handily, for reference, some old issues have been archived at the official city website here. (Although keep in mind that info can be outdated even by the time they go to press!)
A similar helpful publication, available for free from the city's official tourist office when you're in town but now also lives on the web, is Un Ospite di Venezia, or in English, A Guest in Venice.