On May i, 2009 (Italian Labor Day), what will be open in Venice? I know banks/museums/some restaurants will be closed, but will Vaporettos be available to the lagoon/islands? Will churches be closed? Is that just a "lost day" for tourists?
The vaporetti should be on weekend/holiday schedules, but running. I'd assume the churches will be open.
Things will still be open on May 1. You may want to stay in one city that day, because there could be train or airport strikes. There could also be labor protests in various cities. Don't worry they are peaceful. But like the previous person said, local vaporettos will be open. Not much slows venice down in the tourist season.