We just got back from our Greek Island cruise and stayed at a great B&B in Venice. It's called Locanda Orseolo. It is a family run B&B, about 18 rooms total. Very nicely decorated. Amazing people working there. They are friendly, warm, welcoming and extremely helpful with recos for dinner, directions, etc.
They are located about 2 minutes outside of Piazza San Marco but are located in a private courtyard and it's so quiet that you'd think you were miles away from the hustle and bustle of the Piazza.