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.
We would definitely stay there again.
The link to their website is... http://www.locandaorseolo.com/