We will arrive in Florence April 15-18, again 22-23, and Venice on April 20-21. Does anyone know if there are special municipal festivals/events, and how to find out about them?
You might e-mail the TI offices in Florence and Venice to inquire, or check their websites. Florence website lists dozens of 2011 events. Rick includes information about the TI offices in his Italy guidebooks.
Here's one resource: http://www.veniceconnected.com/events. And as mentioned, the TIs will have lists when you arrive.