My wife and I recently visited Venice and stayed at the B&B Corte Campana. We use Rick's guide books almost every where we go in Europe and this B&B is probably one of his best recommendations we've found.
It's about a 2 minute walk from Piazza San Marco. Ricardo and Grace were fantastic hosts. We were shown where the best restaurants are as well as where to get the best gelato!
The rooms are located overlooking a private courtyard - thus making for the quietest 3 nights we had all vacation.
We can't say enough positive things about Corte Campana!